VCA810_12 TI1 | Alldatasheet
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+5V /c45 5V VOUT VC 0 2V/c174 /c45 /c45 /c174 40dB +40dB Gain VCA810 V/c45 Gain Adjust VCA810 www.ti.com SBOS275F –JUNE 2003–REVISED DECEMBER 2010 HighGainAdjustRange,Wideband, VARIABLEGAINAMPLIFIER Check forSamples: VCA810 Operatingfrom±5V supplies,thegaincontrolvoltage1FEATURES fortheVCA810 willadjustthegainfrom–40dB at0V 2• HIGH GAIN ADJUST RANGE: ±40dB inputto +40dB at –2V input.Increasingthe control• DIFFERENTIAL IN/SINGLE-ENDED OUT voltageabove groundwillattenuatethesignalpathto greaterthan 80dB. Signalbandwidthand slew rate• LOW INPUT NOISE VOLTAGE: 2.4nV/√Hz remain constantover the entiregain adjustrange.• CONSTANT BANDWIDTH vs GAIN: 35MHz This 40dB/V gain controlisaccuratewithin±1.5dB• HIGH dB/V GAIN LINEARITY: ±0.3dB (±0.9dB forhigh grade),allowingthe gain control
- GAIN CONTROL BANDWIDTH: 25MHz voltagein an AGC applicationto be used as a Received Signal Strength Indicator(RSSI) with• LOW OUTPUT DC ERROR: < ±40mV ±1.5dBaccuracy.• HIGH OUTPUT CURRENT: ±60mA Excellent common-mode rejection and• LOW SUPPLY CURRENT: 24.8mA common-mode input range at the two(max for−40°C to+85°C temperaturerange) high-impedanceinputsallowtheVCA810 toprovidea differentialreceiveroperationwithgain adjust.TheAPPLICATIONS outputsignalisreferencedtoground.Zero differential
- OPTICAL RECEIVER TIME GAIN CONTROL inputvoltagegivesa 0V outputwitha smalldc offset error.Low inputnoisevoltageensures good output• SONAR SYSTEMS SNR atthehighestgainsettings.• VOLTAGE-TUNABLE ACTIVE FILTERS
- LOG AMPLIFIERS In applicationswhere pulse edge informationis critical,and the VCA810 isbeing used to equalize• PULSE AMPLITUDE COMPENSATION varyingchannelloss,minimalchange ingroup delay• AGC RECEIVERS WITH RSSI over gain settingwillretainexcellentpulse edge• IMPROVED REPLACEMENT FOR VCA610 information. An improvedoutputstageprovidesadequate output currentto drivethe most demanding loads.While principallyintended to drive analog-to-digital converters(ADCs) or second-stageamplifiers,the ±60mA output current will easily drive doubly-terminated50Ω linesor a passivepost-filter stageoverthe±1.7Voutputvoltagerange. VCA810 RELATED PRODUCTS GAIN ADJUST INPUT SIGNAL RANGE NOISE BANDWIDTH SINGLES DUALS (dB) (nV/√Hz) (MHz) VCA811 — 80 2.4 80 — VCA2612 45 1.25 80 — VCA2613 45 1 80 — VCA2614 45 3.6 40DESCRIPTION — VCA2616 45 3.3 40 The VCA810 isa dc-coupled,wideband,continuously VCA2618 45 5.5 30 variable,voltage-controlledgainamplifier.Itprovides a differentialinputtosingle-endedoutputconversion witha high-impedancegaincontrolinputused tovary thegainovera –40dB to+40dB rangelinearindB/V. Pleasebe aware thatan importantnoticeconcerningavailability,standardwarranty,and use incriticalapplicationsofTexas Instrumentssemiconductorproductsand disclaimerstheretoappearsattheend ofthisdatasheet. 2Alltrademarksarethepropertyoftheirrespectiveowners. PRODUCTION DATA informationiscurrentas ofpublicationdate. Copyright© 2003–2010,Texas InstrumentsIncorporatedProductsconform to specificationsper the terms of the Texas Instrumentsstandardwarranty.Productionprocessingdoes not necessarilyincludetestingofallparameters.
Control, VC /c45VS +VS /c45In A (1) VOUT VCA810 GND +In NC (2) VCA810 SBOS275F –JUNE 2003–REVISED DECEMBER 2010 www.ti.com This integratedcircuitcan be damaged by ESD. Texas Instrumentsrecommends thatallintegratedcircuitsbe handled with appropriateprecautions.Failuretoobserveproperhandlingand installationprocedurescan cause damage. ESD damage can rangefromsubtleperformancedegradationtocompletedevicefailure.Precisionintegratedcircuitsmay be more susceptibletodamage because verysmallparametricchanges couldcause thedevicenottomeet itspublishedspecifications. ORDERING INFORMATION (1) SPECIFIED PACKAGE TEMPERATURE PACKAGE ORDERING TRANSPORT PRODUCT PACKAGE-LEAD DESIGNATOR RANGE MARKING NUMBER MEDIA, QUANTITY VCA810ID Rails,75 VCA810ID SO-8 D –40°C to+85°C VCA810 VCA810IDR Tape and Reel,2500 VCA810AID Rails,75 VCA810AID SO-8 D –40°C to+85°C VCA810A (2) VCA810AIDR Tape and Reel,2500 (1) Forthemost currentpackage and orderinginformationsee thePackage OptionAddendum attheend ofthisdocument,orsee the deviceproductfolderatwww.ti.com. (2) The A indicatinghighgradeappearsoppositethepin1 markingindicator. ABSOLUTE MAXIMUM RATINGS (1) Over operatingfree-airtemperaturerange,unlessotherwisenoted. VCA810 UNIT Power supply ±6.5 V Internalpower dissipation See ThermalAnalysissection Differentialinputvoltage ±VS V Inputcommon-mode voltagerange ±VS V Storagetemperaturerange,D package –65 to+125 °C Junctiontemperature(TJ) +150 °C Human body model (HBM) 2000 V ESD ratingsCharge devicemodel (CDM) 1500 V Machine model 200 V (1) Stressesabove theseratingsmay cause permanentdamage. Exposuretoabsolutemaximum conditionsforextendedperiodsmay degradedevicereliability.These arestressratingsonly,and functionaloperationofthedeviceattheseorany otherconditionsbeyond thosespecifiedisnotimplied. PIN CONFIGURATIONS D PACKAGE SO-8 (TOP VIEW) (1) Highgradeversionindicator. (2) NC = Not connected.
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www.ti.com SBOS275F –JUNE 2003–REVISED DECEMBER 2010 ELECTRICAL CHARACTERISTICS: VS = ±5V Boldfacelimitsaretestedat+25°C. AtR L = 500Ω,and VIN = single-endedinputon V+ withV− atground,,unlessotherwisenoted. VCA810 MIN/MAX OVER TYP TEMPERATURE 0°C to –40°C to MIN/ TEST PARAMETER CONDITIONS +25°C +25°C (2) +70°C (3) +85°C (3) UNITS MAX LEVEL (1) AC PERFORMANCE Small-signalbandwidth(seeFigure29) −2V ≤ VC ≤ 0V 35 30 29 29 MHz min B Large-signalbandwidth VO = 2VPP ,−2 ≤ VC ≤ −1 35 30 29 29 MHz min B Frequencyresponsepeaking VO < 500mV PP ,−2V ≤ VC ≤ 0V 0.1 0.5 0.5 0.5 dB min B Slew rate VO = 3.5VStep,−2 ≤ VC ≤ −1,10% to90% 350 300 300 295 V/ms min B Settlingtimeto0.01% VO = 1V Step,−2 ≤ VC ≤ −1 30 40 41 41 ns min B Rise-and-falltime VO = 1V Step,−2 ≤ VC ≤ −1 10 12 12.1 12.1 ns min B Group delay G = 0dB,VC =−1V,f= 5MHz, VO = 500mV PP 6.2 ns typ C Group delayvariation VO < 500mV PP ,−2V ≤ VC ≤ 0V,f= 5MHz 3.5 ns typ C Harmonicdistortion Second harmonic VO = 1VPP ,f= 1MHz, VC = −1V,G = 0dB –71 –51 –50 –49 dBc min B Thirdharmonic VO = 1VPP ,f= 1MHz, VC = −1V,G = 0dB −35 –34 –32 –29 dBc min B Inputvoltagenoise VC = −2V 2.4 2.8 3.4 3.5 nV/√Hz max B Inputcurrentnoise −2V ≤ VC ≤ 0V 1.4 1.8 2.0 2.1 pA/√Hz max B Fullyattenuatedfeedthrough f≤ 1MHz, VC > +200mV −80 −70 dB max B Overdriverecovery VIN = 2V to0V,VC = −2V,G = 40dB 100 150 ns min B DC PERFORMANCE Single-endedordifferentialinput Outputoffsetvoltage(bothinputs −2V ≤ VC ≤ 0V ±4 ±22 ±30 ±32 mV max Agrounded)(4) Outputoffsetvoltagedrift ±125 ±125 V/°C max B Inputoffsetvoltage(4) Bothinputsgrounded ±0.1 ±0.25 ±0.30 ±0.35 mV max A inputoffsetvoltagedrift ±1 ±1.2 mV/°C max B Inputbiascurrent −2V ≤ VC ≤ 0V −6 –10 −12 −14 mA max A Inputbiascurrentdrift ±25 ±30 nA/°C max B Inputoffsetcurrent −2V ≤ VC ≤ 0V ±100 ±600 ±700 ±800 nA max A Inputoffsetcurrentdrift ±1.4 ±2.2 nA/°C max B INPUT Common-mode inputrange ±2.4 ±2.3 ±2.3 ±2.2 V min A Common-mode rejectionratio VCM = 0.5V,VC = −2V,Input-referred 95 85 83 80 dB min A Inputimpedance VCM = 0V,Single-ended 1||1 M Ω ||pF typ C VCM = 0V,Differential > 10 ||< 2 M Ω ||pF typ C Differentialinputrange(5) VC = 0V,VCM = 0V 3 VPP typ C OUTPUT Voltageoutputswing VC = −2V,R L = 100Ω ±1.8 ±1.7 ±1.4 ±1.3 V min A Outputcurrent VO = 0V ±60 ±40 ±35 ±32 mA min A Outputshort-circuitcurrent VO = 0V ±120 mA typ C Outputimpedance VO = 0V,f< 100kHz 0.2 Ω typ C (1) Testlevels:(A)100% testedat+25°C. Over temperaturelimitssetby characterizationand simulation.(B)Limitssetby characterization and simulation.(C)Typicalvalue;onlyforinformation. (2) Junctiontemperature= ambientfor+25°C testedspecifications. (3) Junctiontemperature= ambientatlowtemperaturelimit;junctiontemperature= ambient+30°C athightemperaturelimitforover temperaturespecifications. (4) Totaloutputoffsetis:(OutputOffsetVoltage± InputOffsetVoltagex Gain). (5) Maximum inputatminimum gainfor< 1dB gaincompression. Copyright© 2003–2010,Texas InstrumentsIncorporated SubmitDocumentationFeedback 3 ProductFolderLink(s):VCA810
SBOS275F –JUNE 2003–REVISED DECEMBER 2010 www.ti.com ELECTRICAL CHARACTERISTICS: VS = ±5V (continued) Boldfacelimitsaretestedat+25°C. AtR L = 500Ω,and VIN = single-endedinputon V+ withV− atground,,unlessotherwisenoted. VCA810 MIN/MAX OVER TYP TEMPERATURE 0°C to –40°C to MIN/ TEST PARAMETER CONDITIONS +25°C +25°C (2) +70°C (3) +85°C (3) UNITS MAX LEVEL (1) GAIN CONTROL (VC ,Pin 3) Single-endedordifferentialinput Specifiedgainrange ΔVC /ΔdB = 25mV/dB ±40 dB typ C Maximum controlvoltage G = −40dB 0 V typ C Minimum controlvoltage G = +40dB –2 V typ C Gain drift −1.8V≤ VC ≤ −0.2V ±0.02 ±0.03 dB/°C max B VC < −1.8V,VC > −0.2V ±0.03 ±0.04 dB/°C max B Gain controlslope –40 db/V typ C Gain controllinearity(6) −1.8V≤ VC ≤ 0V ±0.3 ±1 ±1.1 ±1.2 dB max A Gain controlbandwidth 25 20 19 19 MHz min B Gain controlslewrate 80dB Gain Step 900 dB/ns typ C Gain settlingtime 1%, 80dB Step 0.8 ms typ C Inputbiascurrent VC = −1V –1.5 –3.5 –4.5 –8 mA max A Gain + Power-supplyrejectionratio VC = −2V,G = +40dB, +VS = 5V ±0.5V 0.5 1.5 1.8 2 dB/V max A Gain – Power-supplyrejectionratio VC = −2V,G = +40dB, –VS = –5V ±0.5V 0.7 1.5 1.8 2 dB/V max A POWER SUPPLY Specifiedoperatingvoltage ±5 V typ C Minimum operatingvoltage ±4 ±4 ±4 V min A Maximum operatingvoltage ±6 ±6 ±6 V max A Positivesupplyquiescentcurrent Maximum quiescentcurrent +VS = +5V, G = −40dB 10 12.5 12.6 12.7 mA min A Minimum quiescentcurrent +VS = +5V, G = −40dB 10 7.5 7.2 7.1 mA max A Maximum quiescentcurrent +VS = +5V, G = +40dB 18 20.5 22 22.3 mA min A Minimum quiescentcurrent +VS = +5V, G = +40dB 18 15.5 14.5 13.5 mA max A Negativesupplyquiescentcurrent(7) Maximum quiescentcurrent −VS = −5V,G = −40dB 12 14.5 14.6 14.7 mA max A Minimum quiescentcurrent −VS = −5V,G = −40dB 12 9.5 9.4 9.3 mA min A Maximum quiescentcurrent −VS = −5V,G = +40dB 20 22.5 24.5 24.8 mA max A Minimum quiescentcurrent −VS = −5V,G = +40dB 20 17.5 16.5 16 mA min A Positivepower-supplyrejectionratio(+PSRR) Input-referred,VC = −2V 90 75 75 73 dB min A Negativepower-supplyrejectionratio Input-referred,VC = −2V 85 70 70 68 dB min A(–PSRR) THERMAL CHARACTERISTICS Specifiedoperatingrange,ID package –40 to+85 °C typ C Thermalresistance,q JA Junction-to-ambient D SO-8 80 °C/W typ C (6) Maximum deviationfrombestlinefit. (7) Magnitude.
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www.ti.com SBOS275F –JUNE 2003–REVISED DECEMBER 2010 HIGH GRADE DC SPECIFICATIONS: VS = ±5V (VCA810AID) Boldfacelimitsaretestedat+25°C. AtR L = 500Ω,and VIN = single-endedinputon V+ withV− atground,,unlessotherwisenoted. VCA810AID MIN/MAX OVER TYP TEMPERATURE 0°C to –40°C to MIN/ TEST PARAMETER CONDITIONS +25°C +25°C (2) +70°C (3) +85°C (3) UNITS MAX LEVEL (1) DC PERFORMANCE Single-endedordifferentialinput Outputoffsetvoltage −2V < VC < 0V ±4 ±14 ±24 ±26 mV max A Inputoffsetvoltage ±0.1 ±0.2 ±0.25 ±0.3 mV max A Inputoffsetcurrent ±100 ±500 ±600 ±700 mA max A GAIN CONTROL (VC ,Pin 3) Single-endedordifferentialinput POWER SUPPLY Positivesupplyquiescentcurrent Maximum quiescentcurrent +VS = +5V, G = −40dB 10 11.5 11.6 11.7 mA min A Minimum quiescentcurrent +VS = +5V, G = −40dB 10 8.5 8.2 8.1 mA max A Maximum quiescentcurrent +VS = +5V, G = +40dB 18 19.5 21 21.3 mA min A Minimum quiescentcurrent +VS = +5V, G = +40dB 18 16.5 15.5 14.5 mA max A Negativesupplyquiescentcurrent(5) Maximum quiescentcurrent −VS = −5V,G = −40dB 12 14 14.1 14.2 mA min A Minimum quiescentcurrent −VS = −5V,G = −40dB 12 10 9.9 9.8 mA max A Maximum quiescentcurrent −VS = −5V,G = +40dB 20 22 24 24.3 mA min A Minimum quiescentcurrent −VS = −5V,G = +40dB 20 18 17 16.5 mA max A (1) Testlevels:(A)100% testedat+25°C. Over temperaturelimitssetby characterizationand simulation.(B)Limitssetby characterization and simulation.(C)Typicalvalue;onlyforinformation. (2) Junctiontemperature= ambientfor+25°C testedspecifications. (3) Junctiontemperature= ambientatlowtemperaturelimit;junctiontemperature= ambient+30°C athightemperaturelimitforover temperaturespecifications. (4) Maximum deviationfrombestlinefit. (5) Magnitude. Copyright© 2003–2010,Texas InstrumentsIncorporated SubmitDocumentationFeedback 5 ProductFolderLink(s):VCA810
/c45 /c45 /c45 Gain (dB) Frequency (MHz) 1 10 100 1000 V = 10mV , V = 1VIN PP OUT PP V = 100m , V V V = 1IN PP OUT PP V = 1 , V V V = 1IN PP OUT PP V = 2 , VV V = 200mOUT PP IN PP V = 2 , VV V = 20mOUT PP IN PP Frequency (MHz) 1 10 100 R = 500 /c87L V = 1V/c45 + 10mVC DC PP 18/c45 /c45 /c45 /c45 /c45 /c45 Gain (dB) Time (20ns/div) V = 2VIN PPG = 20dB/c45 G = 40dB/c45 Output Voltage (mV) 150 100 100 150/c45 /c45 /c45 Time (20ns/div) V = 10mVIN PPG = +40dB G = +20dB Output Voltage (V) 0.6 0.4 0.2 0.2 0.4 0.6 /c45 /c45 /c45 1.2 1.0 0.8 0.6 0.4 0.2 0.2/c45 Output Voltage (V) Time (20ns/div) G = 0dB to 40dB, V = 1V/c45 IN DC G = 0dB to +40dB, V = 10mVIN DC 100 /c45 /c45 /c45 /c45 /c45 Gain (dB) Control Voltage, V (V)C Specified Operating Range Output Disabled for +0.15V V/c163 /c163 +2VC VCA810 SBOS275F –JUNE 2003–REVISED DECEMBER 2010 www.ti.com TYPICAL CHARACTERISTICS: VS = ±5V AtR L = 500Ω and VIN = single-endedinputon V+ withV− atground,unlessotherwisenoted. SMALL −SIGNAL FREQUENCY RESPONSE GAIN CONTROL FREQUENCY RESPONSE Figure1. Figure2. ATTENUATED PULSE RESPONSE HIGH GAIN PULSE RESPONSE Figure3. Figure4. GAIN CONTROL PULSE RESPONSE GAIN vs CONTROL VOLTAGE Figure5. Figure6.
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Frequency (MHz) 0.1 1 10 G = 0dB, Third Harmonic G = +40dB, Third Harmonic G = 0dB, Second Harmonic G = +40dB, Second Harmonic V = 1VO PP R = 500 /c87L /c45 30 /c45 /c45 /c45 /c45 /c45 /c45 /c45 /c45 /c45 Harmonic Distortion (dBc) Load ( )/c87 100 1000 G = 0dB, Third Harmonic G = +40dB, Third Harmonic G = 0dB, Second Harmonic G = +40dB, Second Harmonic f = 1MHz V = 1VO PP R = 500 /c87L /c45 20 /c45 /c45 /c45 /c45 /c45 /c45 Harmonic Distortion (dBc) Output Voltage (V )PP G = 0dB, Third Harmonic G = +40dB, Second Harmonic G = 0dB, Second Harmonic G = +40dB, Third Harmonic f = 1MHz R = 500 /c87L /c45 20 100 /c45 /c45 /c45 /c45 /c45 /c45 /c45 /c45 Harmonic Distortion (dBc) Gain (dB) 0 5 10 15 20 25 30 35 40 Third Harmonic f = 1MHz V = 1VO PP R = 500 /c87L Second Harmonic /c45 20 /c45 /c45 /c45 /c45 /c45 /c45 Harmonic Distortion (dBc) Gain (dB) /c4540 /c4530 /c4520 /c4510 0 10 20 30 40 Max Useful Input Voltage RangeResulting Output Voltage Input and Output Measured at 1dB Compression Resulting Input Voltage Max Useful Output Voltage Range Input Limited Output Limited 0.1 0.01 Input/Output Voltage (V ) PP Attenuation (dB) /c45 40 /c45 35 /c45 30 /c45 25 /c45 20 /c45 15 /c45 10 /c45 5 0 f = 1MHz V = 1VIN PP R = 500 /c87L Third Harmonic Second Harmonic /c45 20 /c45 /c45 /c45 /c45 /c45 /c45 Harmonic Distortion (dBc) VCA810 www.ti.com SBOS275F –JUNE 2003–REVISED DECEMBER 2010 TYPICAL CHARACTERISTICS: VS = ±5V (continued) AtR L = 500Ω and VIN = single-endedinputon V+ withV− atground,unlessotherwisenoted. HARMONIC DISTORTION vs FREQUENCY HARMONIC DISTORTION vs R LOAD Figure7. Figure8. HARMONIC DISTORTION vs OUTPUT VOLTAGE HARMONIC DISTORTION vs GAIN Figure9. Figure10. INPUT/OUTPUT RANGE vs GAIN HARMONIC DISTORTION vs ATTENUATION Figure11. Figure12. Copyright© 2003–2010,Texas InstrumentsIncorporated SubmitDocumentationFeedback 7 ProductFolderLink(s):VCA810
Frequency (Hz) 100 1k 10k 100k 1M 10M Current Noise (1.8pA/ Hz)/c214 Each Input Differential Input Voltage Noise (2.4nV/ Hz)/c214 e (nV/ )n Hz i (pA/ )n Hz/c63 /c63 Control Voltage (V) Input-Referred Voltage Noise Density Output-Referred Voltage Noise Density R = 20 /c87S on Each Input 10000 1000 100 e (nV/ )n Hz e (nV/ )O Hz/c63 /c63 Frequency (Hz) 1M 10M 100M V = +0.1VC V = +0.2VC 100 120 /c45 /c45 /c45 /c45 /c45 /c45 Isolation (dB) Gain (dB) /c4540 /c4530 /c4520 /c4510 0 10 20 30 40 Maximum Error Band Typical Devices 50/c45 /c45 /c45 /c45 /c45 Output Offset Error (mV) Control Voltage (V) 0 /c450.5 /c451 /c451.5 /c452 Deviation from 40dB/V Gain Slope/c45 0.4 0.3 0.2 0.1 0.1 0.2 0.3 0.4 0.5 /c45 /c45 /c45 /c45 /c45 Gain Error (dB) T otal T ested = 1462 G = +40dB Output Offset Voltage (mV) 250 200 150 100 Count VCA810 SBOS275F –JUNE 2003–REVISED DECEMBER 2010 www.ti.com TYPICAL CHARACTERISTICS: VS = ±5V (continued) AtR L = 500Ω and VIN = single-endedinputon V+ withV− atground,unlessotherwisenoted. NOISE DENSITY vs CONTROL VOLTAGE INPUT VOLTAGE AND CURRENT NOISE Figure13. Figure14. OUTPUT OFFSET VOLTAGE FULLY ATTENUATED ISOLATION vs FREQUENCY TOTAL ERROR BAND vs GAIN Figure15. Figure16. TYPICAL GAIN ERROR PLOT OUTPUT OFFSET VOLTAGE DISTRIBUTION Figure17. Figure18.
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Gain (dB) /c45 40 /c45 30 /c45 20 /c45 10 0 10 20 30 40 V = 1VO PP R = 500 /c87L 1MHz 5MHz 10MHz Group Delay (ns) Frequency (MHz) 1 10 100 V = 1VO PP R = 500 /c87L G = 0dB G = +40dB Group Delay (ns) Time (100ns/div) VOUT 10x VIN 2.5 2.0 1.5 1.0 0.5 0.5 1.0 1.5 2.0 2.5/c45 /c45 /c45 /c45 /c45 Input/Output Voltage (V) Time (100ns/div) VOUT VIN 200 25/c45 /c45 /c45 /c45 /c45 Input/Output Voltage (mV) Gain (dB) /c4540 /c4530 /c4520 /c4510 0 10 20 30 40 CMRR PSRR Input-Referred110 100 CMRR (dB)PSRR (dB) 110 100 CMRR (dB)PSRR (dB) Frequency (MHz) 0.1 1 10 100 PSRR, G = 0dB CMRR, G = 40dB± PSRR, G = +40dB CMRR, G = 0dB VCA810 www.ti.com SBOS275F –JUNE 2003–REVISED DECEMBER 2010 TYPICAL CHARACTERISTICS: VS = ±5V (continued) AtR L = 500Ω and VIN = single-endedinputon V+ withV− atground,unlessotherwisenoted. GROUP DELAY vs GAIN GROUP DELAY vs FREQUENCY Figure19. Figure20. OVERDRIVE RECOVERY AT MAXIMUM GAIN OVERDRIVE RECOVERY AT MAXIMUM ATTENUATION Figure21. Figure22. COMMON −MODE REJECTION RATIO AND COMMON −MODE REJECTION RATIO AND POWER −SUPPLY REJECTION RATIO vs GAIN POWER −SUPPLY REJECTION RATIO vs FREQUENCY Figure23. Figure24. Copyright© 2003–2010,Texas InstrumentsIncorporated SubmitDocumentationFeedback 9 ProductFolderLink(s):VCA810
Frequency (Hz) 1k 10k 100k 1M 10M 100M Gain (dB) Gain (dB) Frequency (Hz) 1k 10k 100k 1M 10M 100M 2/c45 5/c45 /c45 /c45 /c45 Input Bias and Offset Current ( A) /c109 Output Offset Voltage (mA) T emperature ( C)/c176 /c45 50 /c45 25 25 0 50 100 75 125 Output Offset Voltage (V )OS Input Bias Current (I )B 10x Input Offset Current (I )OS Control Voltage (V) 0 /c450.5 /c451.0 /c451.5 /c452.0 Quiescent Current for V/c45 S Quiescent Current for +VS Supply Current (mA) VCA810 SBOS275F –JUNE 2003–REVISED DECEMBER 2010 www.ti.com TYPICAL CHARACTERISTICS: VS = ±5V (continued) AtR L = 500Ω and VIN = single-endedinputon V+ withV− atground,unlessotherwisenoted. GAIN CONTROL +PSRR AT MAX GAIN GAIN CONTROL −PSRR AT MAX GAIN Figure25. Figure26. TYPICAL DC DRIFT vs TEMPERATURE TYPICAL SUPPLY CURRENT vs CONTROL VOLTAGE Figure27. Figure28.
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+5V /c45 5V VOUT VC 0 2V/c174 /c45 /c45 /c174 40dB +40dB Gain VCA810 V/c45 Gain Adjust VCA810 VC VI VO +5V RC RT 25/c87 RL 500/c87
0.1 F/c109
6.8 F/c109
/c45 5V G =(V/V) 10 /c452(V + 1)C VCA810 www.ti.com SBOS275F –JUNE 2003–REVISED DECEMBER 2010
APPLICATION INFORMATION
Thus,G (dB)varieslinearlyoverthespecified−40dB toCIRCUIT DESCRIPTION +40dB rangeas VC variesfrom0V to−2V.Optionally, making VC slightlypositive(≥ +0.15V) effectivelyThe VCA810 isa highgainadjustrange,wideband, disablesthe amplifier,givinggreaterthan 80dB ofvoltageamplifierwith a voltage-controlledgain,as signalpathattenuationatlowfrequencies.shown in Figure 29. The circuit’s basic voltage througha groundedterminationresistororby a direct VCA810 OPERATIONconnectiontoground.The differentialinputstagealso permitsrejectionof common-mode signals.At its Figure30 shows thecircuitconfigurationused as the output, the voltage amplifierpresents a low basis of the ElectricalCharacteristicsand Typical impedance, simplifyingimpedance matching. An Characteristics. Voltage swings reported in the open-loopdesignproduceswidebandwidthatallgain specificationsare taken directlyat the inputand settings. A ground-referenced differentialto outputpins.Fortestpurposes,theinputimpedance is single-endedconversionattheoutputretainsthelow set to 50Ω with a resistanceto ground. A 25Ω outputoffsetvoltage. resistance(RT)isincludedon theV− inputtogetbias currentcancellation.Proper supply bypassing is shown inFigure30,and consistsoftwo capacitorson each supply pin: one large electrolyticcapacitor (2.2mF to 6.8mF),effectiveat lowerfrequencies,and one small ceramic capacitor (0.1mF) for high-frequencydecoupling.For more informationon decoupling,refertotheBoard Layoutsection. Figure29. Block Diagram oftheVCA810 A gaincontrolvoltage,VC ,controlstheamplifiergain magnitudethrougha high-speedcontrolcircuit.Gain polaritycan be eitherinvertingor noninverting, dependingupon theamplifierinputdrivenby theinput signal.The gaincontrolcircuitpresentsthehigh-input impedance ofa noninvertingop amp connection.The controlvoltagepinisreferredtoground as shown in Figure30. VariableGain,Specificationand TestFigure29.The controlvoltageVC variestheamplifier Circuitgainaccordingtotheexponentialrelationship: Noticethatbothinvertingand noninvertinginputsare connected to ground with a resistor(RS and R T).Thistranslatestotheloggainrelationship: Matching the dc source impedance lookingout ofG (dB)= –40 ● (VC + 1)dB. each inputwillminimizeinputoffsetvoltageerror. Copyright© 2003–2010,Texas InstrumentsIncorporated SubmitDocumentationFeedback 11 ProductFolderLink(s):VCA810
t /c45 2V Time-Gain Compensated Control Voltage OPA657 /c45 VB 20k/c87 CF VCA810 CH V = VOUT PEAK R VO 1k/c87 HP5082 50k/c87 2mV to 2V 100kHzRSSI Port 50k/c87 CC 47pF
0.1 VDC
Time (5 s/div)/c109 V = 10mVIN PP V = 100mVIN PPV = 1VIN PP 0.15 0.10 0.05 0.05 0.10 0.15 0.20/c45 /c45 /c45 /c45 Output Voltage (50mV/div) VCA810 SBOS275F –JUNE 2003–REVISED DECEMBER 2010 www.ti.com RANGE-FINDING TGC AMPLIFIER chargingtheholdingcapacitor.Thischargedrivesthe R 2,and C H determinethereleasetimeofthisaction. ResistorR 2 forms a voltagedividerwithR 1, limiting themaximum negativevoltagedevelopedon C H .This limitpreventsinputoverloadof the VCA810 gain controlcircuit. Figure33 shows the AGC response forthe values shown inFigure32. Figure31. TypicalRange-FindingApplication The controlvoltageVC variestheamplifiergainfora basic signal-processingrequirement:compensation for distanceattenuationeffects,sometimes called time-gain compensation (TGC). Time-gain Figure32. 60dB InputRange AGCcompensation increasesthe amplifiergain as the signalmoves throughtheairtocompensate forsignal attenuation.For thispurpose,a ramp signalapplied to the VCA810 gain controlinputlinearlyincreases thedB gainoftheVCA810 withtime. WIDE-RANGE AGC AMPLIFIER The voltage-controlledgain featureof the VCA810 makes this amplifierideal for precisionAGC applicationswithcontrolranges as largeas 60dB. The AGC circuitof Figure32 adds an op amp and diode foramplitudedetection,a hold capacitorto storethecontrolvoltageand resistorsR 1 throughR 3 thatdetermineattackand releasetimes.ResistorR 4 and capacitorC C phase-compensate the AGC feedback loop.The op amp compares the positive peaks of outputVO witha dc referencevoltage,VR . Figure33. AGC Output Voltagefor100kHzWhenever a VO peak exceeds VR , the OPA820 Sinewave at10mV PP ,100mV PP ,and 1VPPoutputswingspositive,forward-biasingthediodeand
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f =W
2 R C/c112W W
1 F/c109
V = VOPEAK R VO 1k/c87 HP5082 50k/c87 CW1 4700pF 100/c87 50k/c87 RW1 300/c87 RW2 300/c87 CW2 4700pF CC 10pF f = 1/2 R C/c112 W1 W1 VC R = RW1 W2 C = CW1 W2 VCA810 www.ti.com SBOS275F –JUNE 2003–REVISED DECEMBER 2010 STABILIZED WEIN-BRIDGE OSCILLATOR magnitude of C W equalsR W , and inspectionof the thisgainreachesthree,oscillationbeginsat fW ; theConnecting the feedback network to the amplifier continuedchargingeffectofR 1 makes theoscillationnoninvertinginputintroducespositivefeedback to amplitudegrow. This growth continuesuntilthatinduce oscillation.The feedback factordisplaysa amplitudereachesa peak valueequalto VR . Then,frequency dependence due to the changing theAGC circuitcounteractstheR 1 effect,controllingimpedances of the C W capacitors.As frequency thepeak amplitudeatVR by holdingtheamplifiergainincreases,the decreasingimpedance of the C W2 at a levelof three.Making VR an ac signal,rathercapacitor increases the feedback factor. than a dc reference,producesamplitudemodulationSimultaneously,the decreasingimpedance of the oftheoscillatoroutput.C W1 capacitordecreasesthisfactor.Analysisshows thatthemaximum factoroccursat Hz, making this the frequency most conducive to oscillation.At this frequency, the impedance Figure34. Amplitude-StabilizedOscillator Copyright© 2003–2010,Texas InstrumentsIncorporated SubmitDocumentationFeedback 13 ProductFolderLink(s):VCA810
G = 10/c452 (V + 1)C /c45 /c45 /c45 /c45 /c45 Output Voltage (V) V /VIN R Voltage Ratio 0.001 0.01 0.1 1 10 100 I II III 470/c87 VCA810 330/c87 VOL VR /c45 10mV OPA820 VIN V = GV/c45OA R CC 50pF 100/c87 V = 1 +/c45 1 + 0.5 Log( V /V )/c45OL IN R( ) VC R R 10/c45 2(V + 1)C V = V = V /c45OA IN R /c183 V =C R V R + R 1 OL 1 2 /c183 V =OL /c45 1 + R R ( ( 1 + 0.5 log/c183/c183 V V IN R ( (/c45 VCA810 SBOS275F –JUNE 2003–REVISED DECEMBER 2010 www.ti.com LOW-DRIFT WIDEBAND LOG AMP produces log-ratiooperation.Eitherway, the log VOA = −GV R ,where . Figure36. TestResultforLOG Amp forVR = −100mVFigure35. Temperature-Compensated Log Response The above VOL expressionreflectsa circuitgain preventany possibilityof an overloadvoltageat theadjuststhegainoftheVCA810 tochange VOA . VC terminal.Such an overloadsaturatestheVCA810 Atequilibrium: gain-controlcircuitry,reducingthe amplifier’s gain. For the feedback connectionof Figure 35, this(1) overloadconditionpermitsa circuitlatch.To prevent this,choose R 1 and R 2 to ensure thatthe op ampThe op amp forcesthisequalityby supplyingthegain cannot possiblydelivera more negativeinputthan −2.5VtotheVC terminal.controlvoltage, . Figure36 exhibitsthreezones ofoperationdescribedCombining the lasttwo expressionsand solvingfor below:VOL yieldsthecircuit’s logarithmicresponse: Zone I:VC > 0V. The VCA810 is operatingin full attenuation(−80dB). The noninvertinginputof the OPA820 willsee ∼0V. VOL is going to be the(2) integrationoftheinputsignal. Optionally,making this voltage a second signal
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G
2 R C/c1122
f =P G = 10/c452 (V + 1)C 330/c87 VCA810 470/c87 VR /c45 10mV VC 500/c87 500/c87 OPA698 VIN VL VI /c45 3.4V +0.5V V = V /c45 x 10OL R /c45 2 R V R + R 1 IN 1 2 +1( ( OPA820 VCA810 VC VO VOA 330/c87 330/c87 C
0.047 F/c109
G
2 R C/c112 2
f =P V V O I R R = /c45 R C G 2 21 + s 1/c183 G = 10 /c45 2 (V + 1)C Input Voltage (V) 0.1 0.01 0.001 Output Voltage (V) f =P G www.ti.com SBOS275F –JUNE 2003–REVISED DECEMBER 2010 Zone III:VC < −2V. The VCA810 controlpinisoutof range,and some measure shouldbe takenso thatit does not exceed –2.5V.A limitingactioncould be VOLTAGE-CONTROLLED LOW-PASS FILTER achievedby usinga voltagelimitingamplifier. InthecircuitofFigure39,theVCA810 servesas the variable-gainelement of a voltage-controlledLOW-DRIFT, WIDEBAND EXPONENTIAL AMP low-pass filter.This sectiondiscusses how this A common use ofthelogamp above involvessignal implementationexpands the circuitvoltageswing compounding. The inverse function, signal capabilityover that normally achieved with the expanding,requiresan exponentialtransferfunction. equivalentmultiplierimplementation.The circuit The VCA810 produces thislatterresponse directly, response pole responds to controlvoltage VC as shown inFigure37. DC referenceVR againsets accordingtotherelationshipinEquation3: the amplifierinputvoltage,and the inputsignalVIN now drivesthegaincontrolpoint.ResistorsR 1 and R 2 (3)attenuatethisdriveto preventoverloadingthe gain controlinput.Settingthese resistorsat the same wherevalues as in the precedinglog amp produces an exponentialamplifierwiththe inversefunctionof the With the components shown, the circuitprovidesalogamp. linearvariationof the low-passcutofffrom 300Hz to 1MHz. Figure37. ExponentialAmplifier Testingthe circuitgiven in Figure 37 gives the exponentialresponseshown inFigure38. Figure39. Tunable Low-Pass Filter The responsecontrolresultsfromamplificationofthe feedback voltageappliedto R 2. First,considerthe case where the VCA810 producesG = 1. Then, the circuitperformsas ifthisamplifierwere replacedby a short circuit.Visuallydoing so leaves a simple voltageamplifierwitha feedbackresistorbypassed by a capacitor.Thisbasiccircuitproducesa response poleat .Figure38. ExponentialAmplifierResponse Copyright© 2003–2010,Texas InstrumentsIncorporated SubmitDocumentationFeedback 15 ProductFolderLink(s):VCA810
G
2 GR C/c112 1
fZ ≈ f =P G fZ ≈ 1
2 R C/c1121
fZ ≈ 1
2 R GC/c1121
Frequency (Hz) 10k 100k 1M 10M V = 1.4V/c45C V = 2V/c45C V = 1.6V/c45C V = 1.8V/c45C 15/c45 /c45 /c45 /c45 /c45 Gain (dB) OPA846 VCA810 VC50/c87 50/c87 OPA820 VOA C
2 F/c109
fZ ≈ 1 2 (GR + R C)/c112 1 3 with G = 10 /c45 2 (V + 1)C VCA810 SBOS275F –JUNE 2003–REVISED DECEMBER 2010 www.ti.com For G > 1,thecircuitappliesa greatervoltagetoR 2, TUNABLE EQUALIZER increasingthefeedbackcurrentthisresistorsupplies A circuitanalogous to the above low-pass filterto the summing junctionof the OPA820. The produces a voltage-controlledequalizerresponse.increasedfeedbackcurrentproducesthesame result The gain controlprovided by the VCA810 ofas ifR 2 had been decreased in valuein the basic Figure41 variesthiscircuitresponsezero from 1Hzcircuitdescribedabove.Decreasingthe effectiveR 2 to10kHz,accordingtotherelationshipofEquation4:resistancemoves the circuitpole to a higher (4)frequency, producing the response control. To visualizethecircuit’s operation,considera circuit theoverallcircuit’s output.Note thatOPA820 output voltage,VOA , relatesto VO throughthe expression, a responsezeroat . VO = G ● VOA .Thus,a G < 1 limitsthemaximum VO Adding the VCA810 as shown inFigure41 permitsswingtoa valuelessthanthemaximum VOA swing. amplificationofthesignalappliedtocapacitorC, and Figure40 shows thelow-passfrequencyfordifferent produces voltage controlof the frequency fZ. controlvoltages. Amplifiedsignalvoltageon C increasesthe signal currentconducted by the capacitorto the op amp feedbacknetwork.The resultisthesame as ifC had been increasedinvaluetoG C .ReplacingC withthis effectivecapacitancevalue produces the circuit controlexpression . Figure40. Voltage-ControlledLow-Pass Filter Frequency Response Figure41. Tunable Equalizer
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fO = 10/c45 (V + 1)C
2 RC/c112
Frequency (Hz) 1 10 100 1k 10k 100k 1M 10M 100M G = +40dB G = +15dB G = 15dB/c45 G = 40dB/c45 AOL 100 Gain (dB) s + 2 + G R C 2 2 s nRC s nRC/c45V V O I Q = n /c183 10/c45 (V + 1)C VCA810 www.ti.com SBOS275F –JUNE 2003–REVISED DECEMBER 2010 Anotherfactorlimitsthe high-frequencyperformance VOLTAGE-CONTROLLED BAND-PASS oftheresultinghigh-passfilter:thefinitebandwidthof FILTER theop amp. Thislimitsthefrequencydurationofthe The variablegain of the VCA810 also providesequalizerresponse.Limitationssuch as bandwidth voltage controlover the center frequency of aand stabilityareclearlyshown inFigure42. band-pass filter.As shown in Figure43, thisfilter followsfrom the state-variableconfigurationwiththe VCA810 replacingthe invertercommon to that configuration.Variationof the VCA810 gain moves the filter’s centerfrequencythrougha 100:1 range followingtherelationshipofEquation5: (5) As before,variablegain controlsa circuittime constantto varythe filterresponse.The gainof the VCA810 amplifiesorattenuatesthesignaldrivingthe lowerintegratorofthecircuit.Thisamplificationalters the effectiveresistanceof the integratortime constant,producingtheresponseofEquation6: Figure42. AmplifierNoise Gain and A OL for DifferentGain (6) Evaluationof this response equation reveals aOther limitationsof thiscircuitare stabilityversus passband gain of AO = –1, a bandwidthof BW =VCA810 gain and inputsignallevelforthe circuit. Figure42 alsoillustratesthese two factors.As the 1/(2pRC), and a selectivityof .NoteVCA810 gainincreases,thecrossoverslopebetween thatvariationof controlvoltageVC altersQ but nottheAOL curveoftheOPA846 and noisegainwillbe bandwidth.greater than 20dB/decade, renderingthe circuit The gainprovidedby theVCA810 restrictstheoutputunstable.The signallevelfor high gain of the swing of the filter.Output signalVO must beVCA810 willmeet two limitations:the outputvoltage constrainedtoa levelthatdoes notdrivetheVCA810swings of both the VCA810 and the OPA846. The output,VOA , intoitssaturationlimit.Note thattheseexpressionVOA = GV I relatesthese two voltages. two outputshave voltageswings relatedby VOA =Thus,an outputvoltagelimitVOAL constrainstheinput G VO .Thus,a swinglimitVOAL imposes a circuitoutputvoltagetoVI ≤ VOAL /G. limitofVOL ≤ VOAL /G.With the components shown, BW = 50kHz. This See Figure44 forthe frequencyresponse fortwobandwidthprovidesan integratorresponse duration differentgain conditionsof the schematicshown inoffourdecades offrequencyforfZ = 1Hz, droppingto Figure43. In particular,noticethe centerfrequencyone decade forfZ = 10kHz. shiftand theselectivityofQ changingas thegainis increased. Copyright© 2003–2010,Texas InstrumentsIncorporated SubmitDocumentationFeedback 17 ProductFolderLink(s):VCA810
R 330/c87 nR 5k/c87 C R 330/c87 50/c87 50/c87 VOA C s nRC s nRC/c45V V O I fO = 10 /c45 (V + 1)C BW = 1 (V + 1)C Q = n /c45 /c183 10 A = 1/c45O /c45 /c45 /c45 /c45 /c45 /c45 /c45 /c45 /c45 /c45 Gain (dB) Frequency (Hz) 100 1k 10k 100k VCA810 SBOS275F –JUNE 2003–REVISED DECEMBER 2010 www.ti.com Figure43. Tunable Band-Pass Filter Figure44. Tunable Band-Pass FilterResponse
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www.ti.com SBOS275F –JUNE 2003–REVISED DECEMBER 2010 DESIGN-IN TOOLS MACROMODELS AND APPLICATIONS SUPPORT DEMONSTRATION BOARDS Computer simulationof circuitperformance using A printedcircuitboard (PCB) isavailabletoassistin SPICE is often useful when analyzing the theinitialevaluationofcircuitperformanceusingthe performanceof analogcircuitsand systems.Thisis VCA810. This evaluationboard (EVM) is available particularlytrueforvideo and RF amplifiercircuits free, as an unpopulated PCB deliveredwith where parasiticcapacitanceand inductancecan play descriptivedocumentation.The summary information a major roleincircuitperformance.A SPICE model forthisboardisshown inTable1. fortheVCA810 isavailablethroughtheTIweb page. The applicationsgroup is also availablefordesign Table1.EVM OrderingInformation assistance.The models availablefrom TI predict typicalsmall-signalac performance,transientsteps,LITERATURE dc performance,and noiseunder a wide varietyofBOARD PART REQUEST PRODUCT PACKAGE NUMBER NUMBER operatingconditions.The models includethe noise VCA810ID SO-8 DEM-VCA-SO-1A SBOU025 terms found in the electricalspecificationsof the relevantproductdatasheet. Go totheTexas Instrumentswebsite(www.ti.com)to requestan evaluationboard through the VCA810 productfolder. OPERATING SUGGESTIONS Outputoverdrivingoccurswhen eitherthe maximum outputvoltageswing or outputcurrentisexceeded.INPUT/OUTPUT RANGE The VCA810 highoutputcurrentof ±60mA ensuresThe VCA810 ’s 80dB gain range allowsthe user to thatvirtuallyalloutputoverdriveswillbe limitedbyhandle an exceptionallywide range of inputsignal voltageswing ratherthanby currentlimiting.Table2levels.If the input and output voltage range summarizestheseoverdriveconditions.specificationsare exceeded, however, signal distortionand amplifieroverdrivewilloccur.The Table2.Output SignalCompressionVCA810 maximum inputand outputvoltagerange is LIMITING TO PREVENT, OPERATEbest illustratedin the TypicalCharacteristicsplot, GAIN RANGE MECHANISM DEVICE WITHIN:Input/OutputRange vs Gain (Figure11).This chart −40dB < G < InputStageplotsinputand outputvoltagesversusgainindB. InputVoltageRange−10dB Overdrive The maximum inputvoltagerangeisthelargestatfull −10dB < G < InternalStage OutputVoltageRangeattenuation(−40dB) and decreases as the gain +10dB Overdrive increases.Similarly,the maximum useful output +5dB < G < OutputStage OutputVoltageRangevoltagerange increasesas theinputdecreases.We +40dB Overdrive can distinguishthreeoverloadingissuesas a resultof the operatingmode: high attenuation,mid-range OVERDRIVE RECOVERYgain-attenuation,and highgain. As shown in the Typical Characteristicsplot,From –40dB to –10dB, gain overdrivingthe input Input/OutputRange vs Gain (Figure11),theonsetofstage isthe onlymethod to overdrivethe VCA810. overdriveoccurswhenever the actualoutputbeginsPreventingthistype of overdriveis achieved by todeviatefromtheidealexpectedoutput.Ifpossible,limitingtheinputvoltagerange. theusershouldoperatetheVCA810 withinthelinear regionsshown inorderto minimizesignaldistortionFrom –10dB to+40dB, overdrivingcan be prevented and overdrivedelay time.However, instancesofby limitingthe outputvoltagerange.There are two amplifieroverdriveare quitecommon in automaticlimitingmechanisms operatinginthissituation.From gain control(AGC) circuits,which involve the–10dB to +10dB, an internalstage is the limiting applicationofvariablegaintoinputsignalsofvaryingfactor;from +10dB to+40dB, theoutputstageisthe levels.The VCA810 designincorporatescircuitrythatlimitingfactor. allowsittorecoverfrom most overdriveconditionsin 200ns or less.Overdriverecoverytimeisdefinedas the time requiredfor the output to returnfrom overdrivetolinearoperation,followingtheremovalof eitheran inputor gain-controloverdrivesignal.The overdriveplotsfor maximum gain and maximum attenuationareshown intheTypicalCharacteristics. Copyright© 2003–2010,Texas InstrumentsIncorporated SubmitDocumentationFeedback 19 ProductFolderLink(s):VCA810
V = V + 10 VOS OSO IOS /c183 G dB ( ( VCA810
1 F/c109 VCV/c45
/c45 /c45 /c45 /c45 /c45 Output Offset Error (mV) Gain (dB) /c4540 /c4530 /c4520 /c4510 0 10 20 30 40 Maximum Error Band Typical Devices VCA810 SBOS275F –JUNE 2003–REVISED DECEMBER 2010 www.ti.com OUTPUT OFFSET ERROR OFFSET ADJUSTMENT Several elements contributeto the output offset Where desired,the offsetof the VCA810 can be voltageerror;among them are the input offset removed as shown inFigure46. Thiscircuitsimply voltage,the output offsetvoltage,the inputbias presentsa dc voltagetoone oftheamplifierinputsto currentand the inputoffsetcurrent.To simplifythe counteractthe offseterrorvoltage.For best offset followinganalysis,the outputoffsetvoltageerroris performance,the trimadjustmentshould be made dependent only on the output-offsetvoltageof the withthe amplifierset at the maximum gain of the VCA810 and the inputoffsetvoltage.The output intended application.The offsetvoltage of the offseterrorcan thenbe expressedas Equation7: VCA810 varieswith gain as shown in Figure45, limitingthe complete offsetcancellationto one selectedgain.Selectingthemaximum gainoptimizes(7) offsetperformance for higher gains where high Where: amplificationof the offseteffectsproduces the greatestoutputoffset.Two featuresminimize the• VOS = Outputoffseterror offsetcontrolcircuitnoisecontributiontotheamplifier• VOSO = Outputoffsetvoltage inputcircuit.First,making theresistanceofR 2 a low• G dB = VCA810 gainindB valueminimizesthe noisedirectlyintroducedby the
- VIOS = Inputoffsetvoltage controlcircuit.This approach reduces both the thermalnoiseoftheresistorand thenoiseproducedThisisshown inFigure45. by theresistorwiththeamplifierinputnoisecurrent.A second noise reductionresultsfrom capacitive bypass of the potentiometeroutput.This reduction filtersout power-supplynoise thatwould otherwise coupletotheamplifierinput. Figure46. OptionalOffsetAdjustment Figure45. Output OffsetErrorversus Gain Thisfilteringactiondiminishesas the wiperposition approaches eitherend of the potentiometer,butThe histogramOutput OffsetVoltageat Maximum practicalconditionspreventsuch settings.Over itsfullGain (Figure18)intheTypicalCharacteristicscurves adjustmentrange,theoffsetcontrolcircuitproducesashows thedistributionfortheoutputoffsetvoltageat ±5mV inputoffsetcorrectionforthe valuesshown.maximum gain. However, theVCA810 onlyrequiresone-tenthofthis range for offset correction,assuring that the potentiometerwiper will always be near the potentiometercenter.Withthissetting,theresistance seen at the wiperremainshigh,which stabilizesthe filteringfunction.
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/c455V EO VCIBI /c45 +5V RS IBN ENI ERS 4kTRS 4kTRT VCA610 VO RP CP VC f =/c45 3dB
2 R C/c112 P P
E = G E + (I R ) + 4kT(R + R )O NI BI T S T + (I R )BN S(V/V)/c183 2 2 2 E = E + (I R ) + 4kT(R + R )N NI BI T S T 2 2 + (I R )BN S VCA810 www.ti.com SBOS275F –JUNE 2003–REVISED DECEMBER 2010 GAIN CONTROL NOISE PERFORMANCE The VCA810 gain is controlledby means of a The VCA810 offers2.4nV/√Hz input-referredvoltage unipolarnegativevoltageappliedbetween ground noiseand 1.8 pA/√Hz input-referredcurrentnoiseat and thegaincontrolinput,pin3.Ifuse oftheoutput a gain of +40dB. The input-referredvoltagenoise, disablefeatureis required,a ground-referenced and the input-referredcurrentnoiseterms,combine bipolarvoltageisneeded. Outputdisableoccursfor to give low outputnoise under a wide varietyof +0.15V ≤ VC ≤ +2V, and producesgreaterthan80dB operatingconditions.Figure48 shows the op amp of attenuation.The controlvoltageshouldbe limited noise analysismodel with all the noise terms to +2V indisablemode, and –2.5V ingainmode in included.In thismodel,allnoiseterms are takento orderto preventsaturationof internalcircuitry.The be noise voltageor currentdensityterms in either VCA810 gain-controlinputhas a –3dB bandwidthof nV/√Hz orpA/√Hz. 25MHz and varieswithfrequency,as shown in the TypicalCharacteristicscurves.Thiswide bandwidth, althoughusefulfor many applications,can allow high-frequencynoise to modulate the gain control input.In practice,thiscan be easilyavoided by filteringthe controlinput,as shown inFigure47. R P should be no greaterthan 100Ω so as not to introducegain errorsby interactingwith the gain controlinputbiascurrentof6mA. Figure48. VCA810 Noise AnalysisModel The totaloutputspotnoisevoltagecan be computed as the square rootof the sum of allsquared output noise voltagecontributors.Equation 8 shows the generalform forthe outputnoisevoltageusingthe Figure47. ControlLineFiltering termsshown inFigure48. (8)GAIN CONTROL AND TEEPLE POINT Dividingthisexpressionby the gain willgive theWhen the VCA810 controlvoltagereaches −1.5V, equivalentinput-referredspot-noisevoltageat thealsoreferredto as the Teeple point, the signalpath noninvertinginputas shown by Equation9.undergoes major changes. From 0V to the Teeple point,thegainiscontrolledby one bank ofamplifiers: (9)a low-gainVCA. As the Teeple pointispassed,the maintainlow totalequivalentinput-referredspot-noise voltage. Copyright© 2003–2010,Texas InstrumentsIncorporated SubmitDocumentationFeedback 21 ProductFolderLink(s):VCA810
T =□T +□P /c180 /c113J D JAA VCA810 SBOS275F –JUNE 2003–REVISED DECEMBER 2010 www.ti.com THERMAL ANALYSIS reduce unwanted capacitance,a window around the b) Minimize the distance (less than 0.25” orOperating junctiontemperature(TJ) is given by 6.35mm) from the power-supply pins toEquation10: high-frequency0.1mF decouplingcapacitors.At the device pins,the ground and power plane layout(10) c) Careful selectionand placement of externalcondition,PDL = VS.2/(4 ● R L), where R L is the components will preserve the high-frequencyresistiveload. high-frequencyapplication.SincetheoutputpinisthePD = 10V(24.8mA)+ 52/(4● 500Ω)= 260.5mW most sensitiveto parasiticcapacitance,alwaysMaximum TJ = +85°C + (0.260W ● +125°C/W) positiontheseriesoutputresistor,ifany,as closeas= 117.6°C possible to the output pin. Other network Thismaximum operatingjunctiontemperatureiswell components,such as invertingor noninvertinginput below most system leveltargets.Most applications terminationresistors,shouldalsobe placedcloseto willbe lower since an absoluteworst-caseoutput thepackage. stagepower was assumed inthiscalculationofVS/2 d) Connections to otherwideband devices on thewhich is beyond the outputvoltagerange forthe board may be made with short directtracesorVCA810. through onboard transmissionlines.For short connections,considerthe traceand the inputto theBOARD LAYOUT next deviceas a lumped capacitiveload.Relatively wide traces (50mils to 100mils, or 1.27mm toAchieving optimum performance with a 2.54mm) shouldbe used,preferablywithgroundandhigh-frequencyamplifiersuch as the VCA810 power planesopened up aroundthem.requirescarefulattentiontoboardlayoutparasiticand externalcomponent types.Recommendations that e)Socketinga high-speedpartlikethe VCA810 iswilloptimizeperformanceinclude: not recommended. The additionallead lengthand pin-to-pincapacitanceintroducedby the socketcana)Minimizeparasiticcapacitancetoany ac ground createan extremelytroublesomeparasiticnetwork,forallofthesignalI/Opins.Thisincludestheground which can make italmost impossibleto achieveapin(pin2).Parasiticcapacitanceon the outputcan smooth,stablefrequencyresponse.Best resultsarecause instability:on both the invertinginputand the obtainedby solderingtheVCA810 ontotheboard.noninvertinginput,it can react with the source impedance to cause unintentionalband limiting.To
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+VS /c45VS Internal Circuitry ESD□Protection□diodes□internally connected□to□all□pins. VCA810 www.ti.com SBOS275F –JUNE 2003–REVISED DECEMBER 2010 INPUT AND ESD PROTECTION present.The diodes can typicallywithstand a continuouscurrentof 30mA withoutdestruction.ToThe VCA810 is builtusing a very high-speed ensure long-termreliability,however, diode currentcomplementarybipolarprocess.The internaljunction should be externallylimitedto 10mA wheneverbreakdown voltagesare relativelylow forthesevery possible.small geometry devices.These breakdowns are reflectedintheAbsoluteMaximum Ratingstable. Allpinson theVCA810 are internallyprotectedfrom ESD by means of a pair of back-to-back, reverse-biaseddiodes to eitherpower supply,as shown inFigure49. These diodesbeginto conduct when thepinvoltageexceeds eitherpower supplyby about0.7V.Thissituationcan occurwithlossofthe amplifierpower supplieswhilea signalsourceisstill Figure49. InternalESD Protection
REVISION HISTORY
NOTE: Page numbers forpreviousrevisionsmay differfrompage numbers inthecurrentversion. Changes from RevisionE (August,2008)toRevisionF Page Changes from RevisionD (February,2006)toRevisionE Page Copyright© 2003–2010,Texas InstrumentsIncorporated SubmitDocumentationFeedback 23 ProductFolderLink(s):VCA810
www.ti.com 28-Sep-2010 Addendum-Page 1 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Qty Eco Plan (2) Lead/ Ball Finish MSL Peak Temp (3) Samples (Requires Login) VCA810AID ACTIVE SOIC D 8 75 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Request Free Samples VCA810AIDG4 ACTIVE SOIC D 8 75 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Request Free Samples VCA810AIDR ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Purchase Samples VCA810AIDRG4 ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Purchase Samples VCA810ID ACTIVE SOIC D 8 75 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Request Free Samples VCA810IDG4 ACTIVE SOIC D 8 75 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Request Free Samples VCA810IDR ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Purchase Samples VCA810IDRG4 ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR Purchase Samples (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
www.ti.com 28-Sep-2010 Addendum-Page 2 Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
*All dimensions are nominal Device Package Type Package Drawing Pins SPQ Reel Diameter (mm) Reel Width W1 (mm) (mm) (mm) (mm) (mm) W (mm) Pin1 Quadrant PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 Pack Materials-Page 1
*All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) VCA810AIDR SOIC D 8 2500 367.0 367.0 35.0 VCA810IDR SOIC D 8 2500 367.0 367.0 35.0 PACKAGE MATERIALS INFORMATION www.ti.com 14-Jul-2012 Pack Materials-Page 2
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