ad706aq Analog Devices, Inc., ad706aq Datasheet - Page 8

• Manufacturer Part Number: ad706aq
• Description: Dual Picoampere Input Current Bipolar Op Amp
• Manufacturer: Analog Devices, Inc.

AD706
1 Hz, 4-Pole, Active Filter
Figure 7 shows the AD706 in an active filter application. An
important characteristic of the AD706 is that both the input bias
current, input offset current, and their drift remain low over
most of the op amp’s rated temperature range. Therefore, for
most applications, there is no need to use the normal balancing
resistor. Adding the balancing resistor enhances performance at
high temperatures, as shown by Figure 8.
Desired Low
Pass Response
Bessel
Butterworth
0.1 dB Chebychev
0.2 dB Chebychev
0.5 dB Chebychev
1.0 dB Chebychev
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.
*WITHOUT THE NETWORK,
PINS 1 AND 2, AND 6 AND 7
OF THE AD706 ARE TIED
TOGETHER.
CAPACITORS C1 AND C2
ARE SOUTHERN ELECTRONICS
MPCC, POLYCARB
INPUT
Table II. 1 Hz, 4-Pole, Low Pass Filter Recommended Component Values
Section 1
Frequency
(Hz)
1.43
1.00
0.648
0.603
0.540
0.492
1M
R1
5%, 50V
1M
R2
Figure 7. 1 Hz, 4-Pole Active Filter
C2
Q
0.522
0.541
0.619
0.646
0.705
0.785
3
2
2M
AD706
R5
C1
+
–
1/2
–V
4
S
0.01 F
0.1 F
1
C5
Section 2
Frequency
(Hz)
1.60
1.00
0.948
0.941
0.932
0.925
–8–
OPTIONAL BALANCE
RESISTOR NETWORKS*
1M
R3
–120
–180
1M
180
120
–60
Figure 8. V
of the 1 Hz Filter
R4
60
Q
0.806
1.31
2.18
2.44
2.94
3.56
0
C4
–40
C3
2M
C1
( F)
0.116
0.172
0.304
0.341
0.416
0.508
5
6
R6
AD706
+V
–
OS
1/2
8
S
vs. Temperature Performance
BALANCE RESISTOR, R3
0
0.01 F
WITHOUT OPTIONAL
C6
7
TEMPERATURE – C
C2
( F)
0.107
0.147
0.198
0.204
0.209
0.206
0.1 F
WITH OPTIONAL BALANCE
40
RESISTOR, R3
C3
( F)
0.160
0.416
0.733
0.823
1.00
1.23
OUTPUT
80
C4
( F)
0.0616
0.0609
0.0385
0.0347
0.0290
0.0242
120
REV. E