OP176GS datasheet(10/21 Pages) AD

10 / 21 page

OP176

REV. 0

–10–

Figure 33. Unity Gain Follower

Figure 34. Unity Gain Inverter

In inverting and noninverting applications, the feedback

resistance forms a pole with the source resistance and capaci-

tance (R

S and CS) and the OP176’s input capacitance (CIN), as

shown in Figure 35. With R

S and RF in the kΩ range, this pole

can create excess phase shift and even oscillation. A small

capacitor, C

FB, in parallel with RFB eliminates this problem.

setting R

S (CS + CIN) = RFB CFB, the effect of the feedback pole is

completely removed.

Figure 35. Compensating the Feedback Pole

Output Voltage Phase Reversal

Since the OP176’s input stage combines bipolar transistors for

low noise and p-channel JFETs for high speed performance, the

output voltage of the OP176 may exhibit phase reversal if either

of its inputs exceeds the specified negative common-mode input

voltage. This might occur in some applications where a trans-

ducer, or a system, fault might apply very large voltages upon

the inputs of the OP176. Even though the input voltage range

of the OP176 is

±10.5 V, an input voltage of approximately

–13.5 V will cause output voltage phase reversal. In inverting

amplifier configurations, the OP176’s internal 7.5 V clamping

diodes will prevent phase reversal; however, they will not

prevent this effect from occurring in noninverting applications.

For these applications, the fix is a 3.92 k

Ω resistor in series

with the noninverting input of the device and is illustrated in

Figure 31.

Figure 31. Output Voltage Phase Reversal Fix

Overdrive Recovery

The overdrive recovery time of an operational amplifier is the

time required for the output voltage to recover to a rated output

level from a saturated condition. This recovery time is impor-

tant in applications where the amplifier must recover quickly

after a large abnormal transient event. The circuit shown in

Figure 32 was used to evaluate the OP176’s overload recovery

time. The OP176 takes approximately 1

µs to recover to V

OUT =

+10 V and approximately 900 ns to recover to V

OUT = –10 V.

Figure 32. Overload Recovery Time Test Circuit

High Speed Operation

As with most high speed amplifiers, care should be taken with

supply decoupling, lead dress, and component placement.

Recommended circuit configurations for inverting and

noninverting applications are shown in Figure 33 and Figure 34.

VIN

909

Ω

VOUT

Ω2.43kΩ

Ω10kΩ

Ω1kΩ

4Vp-p

@ 100Hz

OP176

+15V

10µF

0.1µF

VIN

VOUT

Ω

–15V

10µF

0.1µF

OP176

+15V

10µF

0.1µF

VIN

VOUT

Ω

–15V

10µF

0.1µF

OP176

10pF

4.99k

Ω

2.49k

Ω

4.99k

Ω

CFB

RFB

CIN

VOUT

ΩR

3.92k

Ω

ΩR

Ω

RFB*

VIN

VOUT

*RFB IS OPTIONAL

OP176

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