Datasheet AD706 (Analog Devices) - 8

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AD706 C1 R1 R2 C3 +VS 1M 1M 0.1 F R3 R4 INPUT 3 + 1/2 C2 1M 1M 8 1 5 + AD706 1/2 2 – 4 C4 7 OUTPUT AD706 *WITHOUT THE NETWORK, 0.1 6 – F PINS 1 AND 2, AND 6 AND 7 OF THE AD706 ARE TIED –VS TOGETHER. R6 C6 CAPACITORS C1 AND C2 R5 C5 2M 0.01 F ARE SOUTHERN ELECTRONICS 2M 0.01 F MPCC, POLYCARB 5%, 50V OPTIONAL BALANCE RESISTOR NETWORKS*
Figure 7. 1 Hz, 4-Pole Active Filter
1 Hz, 4-Pole, Active Filter 180 V
Figure 7 shows the AD706 in an active filter application. An important characteristic of the AD706 is that both the input bias
120 WITHOUT OPTIONAL BALANCE RESISTOR, R3
current, input offset current, and their drift remain low over most of the op amp’s rated temperature range. Therefore, for
60
most applications, there is no need to use the normal balancing resistor. Adding the balancing resistor enhances performance at
0
high temperatures, as shown by Figure 8.
WITH OPTIONAL BALANCE RESISTOR, R3 –60 –120 OFFSET VOLTAGE OF FILTER CIRCUIT (RTI) – –180 –40 0 40 80 120 TEMPERATURE – C
Figure 8. VOS vs. Temperature Performance of the 1 Hz Filter
Table II. 1 Hz, 4-Pole, Low Pass Filter Recommended Component Values Section 1 Section 2 Desired Low Frequency Frequency C1 C2 C3 C4 Pass Response (Hz) Q (Hz) Q ( F) ( F) ( F) ( F)
Bessel 1.43 0.522 1.60 0.806 0.116 0.107 0.160 0.0616 Butterworth 1.00 0.541 1.00 1.31 0.172 0.147 0.416 0.0609 0.1 dB Chebychev 0.648 0.619 0.948 2.18 0.304 0.198 0.733 0.0385 0.2 dB Chebychev 0.603 0.646 0.941 2.44 0.341 0.204 0.823 0.0347 0.5 dB Chebychev 0.540 0.705 0.932 2.94 0.416 0.209 1.00 0.0290 1.0 dB Chebychev 0.492 0.785 0.925 3.56 0.508 0.206 1.23 0.0242 NOTE Specified Values are for a –3 dB point of 1.0 Hz. For other frequencies simply scale capacitors C1 through C4 directly, i.e. for 3 Hz Bessel response, C1 = 0.0387 µF, C2 = 0.0357 µF, C3 = 0.0533 µF, C4 = 0.0205 µF. REV. G –8– Document Outline FEATURES APPLICATIONS CONNECTION DIAGRAM GENERAL DESCRIPTION PRODUCT HIGHLIGHTS SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS METALIZATION PHOTOGRAPH TYPICAL PERFORMANCE CHARACTERISTICS 1 HZ, 4-POLE, ACTIVE FILTER OUTLINE DIMENSIONS ORDERING GUIDE REVISION HISTORY