AF100 NSC | Alldatasheet
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a A National 3 AF100 Universal Active Filter General Description Features The AF100 state variable active filter is a general second Military or commercial specifications order lumped RC network. Only four external resistors pro- ™ Independent Q, frequency, gain adjustments gram the AF100 for specific second order functions. Low- _™ Low sensitivity to external component variation pass, highpass, and bandpass functions are available simul- _m Separate lowpass, highpass, bandpass outputs taneously at separate outputs. Notch and allpass functions jg inputs may be differential, inverting, or non-inverting are available by summing the outputs in the uncommitted @ Allpass and notch outputs may be formed using uncom- output summing amplifier. Higher order systems are realized ° ‘amplifier by cascading AF 100 active filters with appropriate program- ming resistors. @ Operates to 10 kHz Any of the classical filter configurations, such as Butter- A range to 500 #8V to #108V worth, Bessel, Cauer, and Chebyshev can be formed. m Power supply range 0 : m Frequency accuracy £1% unadjusted © Q frequency product <50,000 Connection Diagrams Ceramic Dual-In-Line Package Plastic Dual-in-Line Package Mo Wo BANDPASS wep BANDPASS HGHPASS PN PM NT OUTPUT. «=v OUTPUT INPUT GND wri OUTPUT OUTPUT, ssp mUT 6 te 4 tk 12. ii 10. EE 16 NS, 4 i 12. ti NO. oO ri — =n Esmee "TT ma fe en <a [J q 2 g 4 5 6 7 8 0 2 3 4 5 7 g INPUT «= INPUT ~HIGHPASS «= +¥— LOWPASS AMP WT? NO wv MP AMP GND AMP + INT2 LOWPASS ‘ouUT OUIPUT +PUT PM NPT PUT ouput OUTPUT TUKHONI-1 TUK/ONI1-2 Top View ‘*Note: Internally connected. Do not use. Order Number AF100-1CJ or AF100-2CJ Top View ‘See NS Package Number HY13A. Order Number AF100-1CN or AF100-2CN See NS Package Number N16A Metal Can Package on v sanoeass OUTPUT wr PO © OV @ zt (2) Order Number AF100-1CJ, AF100-1G, AF100-2CG or pps AF100-2G [ee] Onn vem —-(@) outrur See NS Package Number H12B <I > of @) ioeass, ~y we om NOY ©) © wu lowpass ve OuuT wz TUK/10111-3 Top View
iL | Absolute Maximum Ratings <| it ilitary/Aerospace specified devices are required, Operating Temperature please contact the National Semiconductor Sales AF100-1CJ, AF100-2CJ, Office/Distributors for availability and specifications. AF100-1CG, AF100-2CG, Supply Voltage +18V AF100-1CN, AF100-2CN —25°C to + 85°C Power Dissipation 900 mW/Package AF100-1G, AF100-2G —55°C to + 125°C (600 mW/Amp) Storage Temperature ° AF100-1G, AF100-2G —65°C to + 125°C Differential Input Voltage ; +36V ‘AF100-10G, AF100-26G, Output Short Circuit Duration (Note 1) Infinite AF100-1Gu, AF100-2CJ, Lead Temperature (Soldering, 10 sec.) 300°C AF100-1CN, AF100-2CN —25°C to + 100°C Electrical Characteristics (compete Active Fitter) (Note 2) Parameter [| conattions win typ | Max | Units Frequency Range fo XQ < 50,000 Le es Q Range fc XQ < 50,000 a ee ee fo Accuracy AF100-1, AF100-1C tc X Qs 10,000, Ta = 25°C #25 % AF100-2, AF100-2C fc X Q< 10,000, Ta = 25°C £1.0 foTemperatureCocticient | TT ts | 150 | ppm Q Accuracy toxasioootranarc | | | 7s | Power Supply Curent Vs = £18V [oes Ts Tima Electrical Characteristics (internat op Amp) (Note 3) Parameter | conaitions [win [tye | Max | Unite Input Offset Voltage [| rsstona [To [eo |v Input Offset Curent Po Input Bias Current Poco 200s Input Resistance a ee Large Signal Voltage Gain Ri 2 2k Vour = +10V vim Output Voltage Swing RL = 10ka £12 £14 Vv RL = 2k +10 +13 Input Voltage Range Poe GommonModeRejectin Ratio | Asstoen | 70 | |S Supply VotageRejectonRao | Agsiokn | 77 |e] | Oupurshortcircuturent fT Tm Slow Rate (Unity Gain) a eS 7 Small Signal Bandwidth a ee ee Phase Margin PT rs Note 1: Any of the amplifiers can be shorted to ground indefinitely, however more than one should not be ‘simultaneously shorted as the maximum junction temperature will be exceeded. Note 2: Specifications apply for Vs = + 15V, over —25°C to +85°C for the AF100-1C and AF100-2C and over ~55°C to +125°C for the AF100-1 and AF100-2, unless otherwise specified. Note 3: Specifications apply for Vg = +15V, Ta = 25°C. 1-6
1 Ret 2 Ree ann ry (lowpass)
105 INTe=e9 4 4 oN
FIGURE 3. Non-Inverting Input
FIGURE 4. inverting Input FIGURE 5. Differential Input
4422 A= 2+ say | — | + 01 won
FIGURE 6. Output Notch Using All Four Amplifiers
14 Cz [ |
14 WE, | + 04 oye w= 1 gy = 08
2 CONTR, eNl ao Rz
11 Ri 1,
1 Ret 2” Bre
FIGURE 7. Input Notch Using Three Amplifiers
FIGURE 8. Allpass
4 RT Rr aT
FIGURE 9. Resistive Tuning Rs RS FIGURE 10. T Tuning
3 A > Son
5 ENS & FO
0.05033 Non-Inverting Input
2 EEE TIN At
FIGURE 11. Low Frequency RC Tuning For Q < Quin in non-inverting mode: FIGURE 12. Q Tuning for Q > Quin,
FIGURE 14. Q Tuning Inverting Input TL/K/10111-25,
2 ECoTINGN = 00K
FIGURE 15. Input RC Notch
be tuned by adding trim pots or trim resistors in series or Pass summing) or the input resistance (input RC). the Q determining resistor. proper resistor is adjusted for a null at the output. the center frequency of the section the lowpass output is tuned through the ni 1 RC input. through pin 1 the phase shift at center frequency will be resistor. ground (Q < 0.6). High Q tuning resistors will be from pin 1 shift between input and bandpass output is 180°. have an output impedance very much lower than the input. . the circuit will see to obtain precise adjustment. ppe equency) ower juency). 1 7 zero resistor for a null at the ouput of the summing amplifier. f= 20) +17 a@) x to fier and adjusting the feedback resistance. and adjust for 45° phase change or a 3 dB gain change. FIGURE 17. Filter Tuning Setup
FIGURE 20. 1010 Hz Notch—Telephone Holding Tone Reject Filter prototype, the filter to be designed is usually reduced to a response which can be defined by four quantities.
| Applications Information (continues) < GRAPH I. Lowpass Prototype Response To obtain the lowpass prototype for the notch filter (Graph 1) Amax and Ain are the same as for the lowpass case and ts —f; Aun fe=1 tgs= S—1 = f4—te $ where fg = Vii fs = Via ty 3 GRAPH L. Notch Response a 4 te fs wx LOG FREQUENCY TUK /10111~-33 Amax = the maximum peak to peak ripple in the passband. Amin = the minimum attenuation in the stopband. ‘a fc = the passband cuttoff frequency. fs = the stopband start frequency. By defining these four quantities for the lowpass prototype thf fy fe fs the normalized pole and zero locations and the Q (quality) TL/K/10111-96 Crone can be determined from tables or by computer fi Transt to To obtain the lowpass prototype for the highpass filt zed Lowpass in the er The normalized lowpass filter has the passband edge nor- (Graph 4) Auaax and Auin are the same as for the lowpass malized to unity. The un-normalized lowpass fiter instead c 2 ane'’s 1 has the passband edge at fc. The normalized and un-nor- GRAPH J. Highpass Response malized lowpass filters are related by the transformation s = Swe. This transforms the normalized passband edge s = 4 j to the un-normalized passband edge s = jwc. a” Normalized Lowpass Transformed to Aux Un-Normalized Highpass. The transformation that can be used for lowpass to high- pass is S = w¢/s. Since S is inversely proportional to s, the Aun low frequency and high frequency responses are inter- changed. The normalized lowpass 1/(S2 + S/Q + 1) trans- forms to the un-normalized highpass ff —_* TUK/10111-34 2+ et 2 To obtain the lowpass prototype for a bandpass filter (Graph Q K) Amax and Ayn are the same as for the lowpass case but Normalized Lowpass Transformed to Un-Normalized fo=1 fe = Soh Bandpass ce Sg fe The transformation that can be used for lowpass to band- where fy = Wits = Vota ie, tric pass is S = (s2 + wo2)/BWs where wo? is the center fre- ere ts = via See x oon atic Symmetry quency of the desired bandpass filter and BW is the ripple is — fy = Amin bandwidtt bandwidth. t4 — fg = Ripple bandwidth Normalized Lowpass Transformed to Un-Normalized GRAPH K. Bandpass Response Bandstop (or Notch) The bandstop filter has a reciprocal response to a bandpass 4 filter. Therefore a bandstop filter can be obtained by first r transforming the lowpass prototype to a highpass and then ux performing the bandpass transformation. SELECTION OF TRANSFER FUNCTION The selection of a function which approximates the shape of Nw the response desired is a complicated process. Except in the simplest cases it requires the use of tables or computer Programs. The form of the transfer function desired is in ftp fy th fs terms of the pole and zero locations. The most common quwrottt-s8 approximations found in tables are Butterworth, Tscheby- 7 cheff, Elliptic, and Bessel. The decision as to which approxi- mation to use is usually a function of the requirements and 1-16
Applications Information (continued) = ‘system objectives. Butterworth filters are the simplest but Maximum output noise s have the disadvantage of requiring high order transfer func- Power consumption tions to obtain sharp roll-offs. Power supply voltage The Tschebycheff function is a min/max approximation in Dynamic range the passband. This approximation has the property that it is 9 equiripple which means that the error oscillates between Maximum output level maximums and minimums of equal amplitude in the pass- The second step is to find the pole and zero location for the band. the Tschebycheff approximation, because of its equi- transfer function which meet the above requirements. This ripple nature, has a much steeper transition region than the can be done by using tables and graphs or network synthe- Butterworth approximation. sis. The form of the transfer function which is easiest to The elliptic filter, also known as Cauer or Zolotarev filters, convert to a cascaded filter is a product of first and second are equiripple in the passband and stopband and have a order terms in these forms: ane transition region than the Butterworth or the Tsche- First Order Second Order ° K For a specific lowpass filter three quantities can be used to —K_ _—_—_ (lowpass) determine the degree of the transfer function: the maximum s+ oR 52+ Ost a2 passband ripple, the minimum stopband attenuation, and Q the transition ratio (tr = wg/ac). Decreasing Amax, in- K ke? creasing Awin, or decreasing tr will increase the degree of Ks (highpass) the transfer function. But for the same requirements the el- stor 32 +g + G2 liptic filter will require the lowest order transfer function. Ta- Q 0 bles and graphs are available in reference books such as “Reference Data for Radio Engineers”, Howard W. Sams & Ks (bandpass) Co., Inc., 5th Edition, 1970 and Erich Christian and Egon 2 4 206 4 woe Eisenmann, “Filter Design Tables and Graphs”, John Wiley tq st eo and Sons, 1966. For specific transfer functions and their pole locations such Ki? + 027) notch text as Louis Weinberg, “Network Analysis and Synthesis”, set 0 s + wo? McGraw Hill Book Company, 1962 and Richard W. Daniels, Q o “Approximation Methods for Electronic Filter Design”, McGraw-Hill Book Company, 1974, are available. 52 — 205 4 ange DESIGN OF CASCADED MULTISECTION FILTERS oa (allpass) The first step in designing is to define the response required 2+ 20g 4 @2 and define the performance specifications: Q 1, Type of filter: Each of the second order functions is realizable by tuning Lowpass, highpass, bandpass, notch, allpass an AF100 stage. By cascading these stages the desired 2. Attenuation and frequency response transfer function is realized. 3. Performance CASCADING SECOND ORDER STAGES | Center frequency/corner frequency plus tolerance and The primary concern in cascading second order stages is to stability minimize the maximum difference in amplitude from input to Insertion loss/gain plus tolerance and stability output over the frequencies of interest. A computer program Sourve impedance is probably required in very complicated cases but some pedal general rules that can be used that will usually give satisfac- Load impedance tory results are: RIPPLE dB (Ayay) xe 7 _ Aun -48 fyHe fg 45 fo Hz fgfy fp He TUK/10111-37 GRAPH M. Generalized Model Response
- If highpass and lowpass stages are cascaded the low- and then additional stages should be added in order of
pass sections should be the higher frequency and high- least difference between first stage Q and their Q. Pass sections the lower frequency. FIGURE 21. Lowpass Elliptic Filter Example
FIGURE 22. Switchable Fitter Example: 500 Hz/ 1000 Hz Butterworth Lowpass
3 COUN
FIGURE 23. EEG Delta Filter—3 Hz Lowpass
FIGURE 25. Test Circuit Block Diagram This design is an example of a 60 Hz notch filter. The re- 1, Design a lowpass “prototype” for the filter. Maximum passband ripple 0.1 dB ter design. 0.1 dB bandwidth 15 Hz max Culate the value of the resistors required to build the filter. ‘identification of data common to several programs.
Applications Information (continued) r=} PROGRAM NO. 2 ENTER FREQUENCY SCALING FACTOR ° (DETERMINES UN-NORMALIZED POLE + ZERO a LOCATIONS OF FIRST SECTION) ENTER THE # OF FILTERS TO BE DESIGNED (DATA ENTERED FROM PROGRAM NO. 1) a RUN ENTER THE C.F. AND BW OF EACH FILTER WHAT TYPE FILTER BANDPASS OR NOTCH 7 60, 15 eee OF POLE PAIRS? 1 OUTPUT OF PROGRAM NO. 2 ? ‘TRANSFORMED POLE/ZERO LOCATIONS ENTER # OF JW AXIS ZEROS? 1 FIRST SECTION ENTER # OF REAL POLES? 0 POLE LOCATIONS ENTER # OF ZEROS AT ZERO? 0 CENTER FREQ. Q ENTER # OF COMPLEX ZEROS? 0 8693601 (From Line 2.3) 11.3813 (From Line 24) ENTER # OF REAL ZEROS? 0 63.228877 (From Line 25) 11.31813 (From Line 26) ENTER F&Q OF EACH POLE PAIR SW AXIS ZEROS ENTER VALUES OF JW AXIS ZEROS 60.533361 (From Line 2.2) PROGRAM NO. 3 (CHECK OF FILTER RESPONSE USING PROGRAM NO. 2 DATA BASE) RUN NUMERATOR [ZEROS] AWSAZ+RWS+Z()A2 1 0 59.471339 (From Line 2.1) 1 0 60.533361 (From Line 2.2) REAL POLE COMPLEX POLE PAIRS F a 1 §6,93601 1.31813 (From Lines 2.3 and 24) 2 63,228877 11.1813 (From Lines 25 and 26) RUN FREQ. ‘obs PHASE DELAY NOR. DELAY FREQ. NOB N PHASE DELAY NOR. DELAY 1-21