REV. C

OP77

–11–

APPLICATIONS INFORMATION

7

2

3

4

6

R2

1M

+15V

0.1 F

–15V

R4

R3

R1

1k

1M

0.1 F

1k

OP77E

Figure 7. Precision High-Gain Differential Amplifier

The high gain, gain linearity, CMRR, and low TCVos of the

OP77 make it possible to obtain performance not previously

available in single-stage very high-gain amplifier applications.

For best CMR,

R

R

1

2

must equal

R

R

3

4

. In this example,

with a 10 mV differential signal, the maximum errors are as listed

in Table I.

Table I. Maximum Errors

TYPE

AMOUNT

COMMON-MODE VOLTAGE

0.01%/V

GAIN LINEARITY, WORST CASE

0.02%

TCVOS

0.003%/

∞C

TCI OS

0.008%/

∞C

2

3

6

INPUT

OP77

+15V

–15V

100

OUTPUT

10pF

0.1 F

0.1 F

4

7

Figure 8. Isolating Large Capacitive Loads

This circuit reduces maximum slew-rate but allows driving

capacitive loads of any size without instability. Because the boon

resistor is inside the feedback loop, its effect on output imped-

ance is reduced to insignificance by the high open-loop gain

of the OP77.

Bilateral Current Source

2

3

6

R2

990

R4

R3

R1

10

OP77

100k

1k

100k

R5

Figure 9. Basic Current Source

2

3

6

R2

R4

R3

R1

OP77

R5

+15V

–15V

2N2907

2N2222

R3

R1 – R5

(

)

GIVEN R3 = R4

R5, R1 = R2

Figure 10. 100 mA Current Source

These current sources will supply both positive and negative

current into a grounded load.

R

R

R

RR

R

R

R

O

=

+

Ê

ËÁ

ˆ

¯˜

+

5

4

2

1

54

2

3

1