OP497AY View Datasheet(PDF) - Analog Devices

Part Name

Description

Manufacturer

OP497AY

Precision Picoampere Input Current Quad Operational Amplifier

Analog Devices 

OP497

OPEN-LOOP GAIN LINEARITY

The OP497 has both an extremely high gain of 2000 V/mv mini-

mum and constant gain linearity. This enhances the precision of

the OP497 and provides for very high accuracy in high closed-loop

gain applications. Figure 5 illustrates the typical open-loop gain

linearity of the OP 497 over the military temperature range.

RL = 10k⍀

VS = ؎15V

VCM = 0V

TA = +125 C

TA = +25C

TA = –55 C

–15 –10

–5

0

5

10

15

OUTPUT VOLTAGE – Volts

Figure 5. Open-Loop Linearity of the OP497

APPLICATIONS

Precision Absolute Value Amplifier

The circuit of Figure 6 is a precision absolute value amplifier

with an input impedance of 30 MΩ. The high gain and low

TCVOS of the OP497 ensure accurate operation with microvolt

input signals. In this circuit, the input always appears as a com-

mon-mode signal to the op amps. The CMR of the OP497

exceeds 120 dB, yielding an error of less than 2 ppm.

+15V

C2

0.1␮F

R1

1k⍀

R3

1k⍀

2

8

C1

30pF

1/4

1

OP497

VIN 3

C3

4 0.1␮F

D1

1N4148

D2

1N4148

6

1/4

7

OP497

5

0V < VOUT < 10V

R2

2k⍀

–15V

Figure 6. Precision Absolute Value Amplifier

PRECISION CURRENT PUMP

Maximum output current of the precision current pump shown

in Figure 7 is ± 10 mA. Voltage compliance is ± 10 V with ± 15 V

supplies. Output impedance of the current transmitter exceeds

3 MΩ with linearity better than 16 bits.

R1

10k⍀

–

VIN

R2

10k⍀

+

R3

10k⍀

2

1/4

OP497

3

R5

1

10k⍀

+15V

R4

10k⍀

IOUT =

VIN

R5

=

VIN

100⍀

=

10mA/ V

85

7 1/4

OP497

6

4

IOUT

؎10mA

–15V

Figure 7. Precision Current Pump

PRECISION POSITIVE PEAK DETECTOR

In Figure 8, the CH must be of polystyrene, Teflon*, or polyeth-

ylene to minimize dielectric absorption and leakage. The droop

rate is determined by the size of CH and the bias current of the

OP497.

2

1/4

1

VIN 1k⍀ 3 OP497

1k⍀

1N4148

2N930

CH

1k⍀

+15V

0.1␮F

6

8

1/4

7

5 OP497

4 0.1␮F

VOUT

1k⍀

RESET

–15V

Figure 8. Precision Positive Peak Detector

SIMPLE BRIDGE CONDITIONING AMPLIFIER

Figure 9 shows a simple bridge conditioning amplifier using

the OP497. The transfer function is:

VOUT

=

VREF





R

∆R

+ ∆R





RF

R

The REF43 provides an accurate and stable reference voltage

for the bridge. To maintain the highest circuit accuracy, RF

should be 0.1% or better with a low temperature coefficient.

*Teflon is a registered trademark of the Dupont Company.

–8–

REV. D

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