AD704 Analog Devices, AD704 Datasheet - Page 12

• Manufacturer Part Number: AD704
• Description: Picoampere Input Current Quad Bipolar Op Amp
• Manufacturer: Analog Devices

Specifications of AD704

• Vcc-vee: 4V to 36V
• Isy Per Amplifier: 600µA
• Packages: DIP,LCC,SOIC
• -3db Bandwidth: 800kHz
• Slew Rate: 150mV/µs
• Vos: 30µV
• Ib: 100pA
• # Opamps Per Pkg: 4
• Input Noise (nv/rthz): 15nV/rtHz

AD704
The 1 Hz, four-pole active filter offers dc precision with a
minimum of components and cost. The low current noise,
I
the 1 μV/°C drift of the AD704. This means that lower capacitor
values can be used, reducing cost and space. Furthermore,
because the AD704’s I
temperature range, most applications do not require the use of
the normal balancing resistor (with its stability capacitor).
Adding the optional balancing resistor enhances performance at
high temperatures, as shown in Figure 36. Table 5 gives
capacitor values for several common low pass responses.
Table 5. 1 Hz, Four-Pole Low-Pass Filter Recommended Component Values
Desired Low Pass
Response
Bessel
Butterworth
0.1 dB Chebychev
0.2 dB Chebychev
0.5 dB Chebychev
1.0 dB Chebychev
1
OS
Specified values are for a −3 dB point of 1.0 Hz. For other frequencies, simply scale the C1 through C4 capacitors directly; that is, for a 3 Hz Bessel response,
C1 = 0.0387 μF, C2 = 0.0357 μF, C3 = 0.0533 μF, and C4 = 0.0205 μF.
, and I
B
allow the use of 1 MΩ resistors without sacrificing
B
is as low as its I
Section 1
Frequency (Hz)
1.43
1.00
0.648
0.603
0.540
0.492
OS
, over most of the MIL
Q
0.522
0.541
0.619
0.646
0.705
0.785
Section 2
Frequency (Hz)
1.60
1.00
0.948
0.941
0.932
0.925
Rev. E | Page 12 of 16
Q
0.806
1.31
2.18
2.44
2.94
3.56
Figure 36. V
1
–120
–180
180
120
–60
60
0
OS
–40
C1 ( µF)
0.116
0.172
0.304
0.341
0.416
0.508
vs. Temperature Performance of the 1 Hz Filter Circuit
BALANCE RESISTOR, R3
BALANCE RESISTOR, R3
0
WITHOUT OPTIONAL
WITH OPTIONAL
TEMPERATURE (°C)
C2 (µF)
0.107
0.147
0.198
0.204
0.209
0.206
40
C3 (µF)
0.160
0.416
0.733
0.823
1.00
1.23
80
120
0.0616
0.0609
0.0385
0.0347
0.0290
0.0242
C4 (µF)