OP1177/OP2177/OP4177

Rev. G | Page 16 of 24

OP1177

6

7

2

3

4

V+

V–

R2

100kΩ

10kΩ

R1

1kΩ

+

–

200mV

Figure 54. Test Circuit for Overload Recovery Time

Figure 18 shows the positive overload recovery time of the

OP1177. The output recovers in less than 4 μs after being

overdriven by more than 100%.

The negative overload recovery of the OP1177 is 1.4 μs, as seen

in Figure 19.

THD + NOISE

The OPx177 has very low total harmonic distortion. This indicates

excellent gain linearity and makes the OPx177 a great choice for

high closed-loop gain precision circuits.

Figure 55 shows that the OPx177 has approximately 0.00025%

distortion in unity gain, the worst-case configuration for distortion.

FREQUENCY (Hz)

100

1k

0.001

0.01

20

6k

0.0001

0.1

BW = 22kHz

Figure 55. THD + N vs. Frequency

CAPACITIVE LOAD DRIVE

OPx177 is inherently stable at all gains and capable of driving

large capacitive loads without oscillation. With no external

compensation, the OPx177 safely drives capacitive loads up to

1000 pF in any configuration. As with virtually any amplifier,

driving larger capacitive loads in unity gain requires additional

circuitry to assure stability.

In this case, a snubber network is used to prevent oscillation

and reduce the amount of overshoot. A significant advantage of

this method is that it does not reduce the output swing because

Figure 56 is a scope shot of the output of the OPx177 in response

to a 400 mV pulse. The load capacitance is 2 nF. The circuit is

configured in positive unity gain, the worst-case condition for

stability.

As shown in Figure 58, placing an R-C network parallel to the

There is no ringing, and overshoot is reduced from 27% to 5%

using the snubber network.

capacitive loads, up to 200 nF. Values for other capacitive loads can

be determined experimentally.

Table 5. Optimum Values for Capacitive Loads

10 nF

20 Ω

0.33 μF

50 nF

30 Ω

6.8 nF

200 nF

200 Ω

0.47 μF

0

GND

TIME (10µs/DIV)

Figure 56. Capacitive Load Drive Without Snubber

GND

TIME (10µs/DIV)

Figure 57. Capacitive Load Drive with Snubber