OP162D 查看數據表（PDF） - Analog Devices

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OP162D

15 MHz Rail-to-Rail Operational Amplifiers

Analog Devices 

OP162/OP262/OP462

2V

100

90

500ns

10

0%

50mV

VS = 5V

AV = 1

RL = 10k⍀

Figure 32. Oscilloscope Photo of VS and VOUT

+1

0 TO +5V +

SQUARE –

OP462

VOUT

10k⍀

Figure 33. Test Circuit for Power On Settling Time

Capacitive Load Drive

The OP162/OP262/OP462 is a high speed, extremely accurate

device and can tolerate some capacitive loading at its output.

As load capacitance increases, however, the unity-gain band-

width of the device will decrease. There will also be an increase

in overshoot and settling time for the output. Figure 35 shows

an example of this with the device configured for unity gain and

driving a 10 kΩ resistor and 300 pF capacitor placed in parallel.

By connecting a series R-C network, commonly called a “snub-

ber” network, from the output of the device to ground, this

ringing can be eliminated and overshoot can be significantly

reduced. Figure 34 shows how to set up the snubber network,

and Figure 36 shows the improvement in output response with

the network added.

+5V

OPx62

VOUT

VIN

RX

CL

CX

Figure 34. Snubber Network Compensation for Capacitive

Loads

VS = 5V

100

AV = 1

90

CL = 300pF

RL = 10k⍀

10

0%

50mV

1␮s

Figure 35. A Photo of a Ringing Square Wave

VS = 5V

100

AV = 1

90

CL = 300pF

RL = 10k⍀

10

0%

50mV

WITH SNUBBER:

RX = 140⍀

CX = 10nF

1␮s

Figure 36. A Photo of a Nice Square Wave at the Output

The network operates in parallel with the load capacitor, CL,

and provides compensation for the added phase lag. The actual

values of the network resistor and capacitor are determined

empirically to minimize overshoot while maximizing unity-gain

bandwidth. Table I shows a few sample snubber networks for

large load capacitors:

Table I. Snubber Networks for Large Capacitive Loads

CLOAD

<300 pF

500 pF

1 nF

10 nF

RX

140 Ω

100 Ω

80 Ω

10 Ω

CX

10 nF

10 nF

10 nF

47 nF

Obviously, higher load capacitance will also reduce the unity-

gain bandwidth of the device. Figure 37 shows a plot of unity-

gain bandwidth versus capacitive load. The snubber network

will not provide any increase in bandwidth, but it will substan-

tially reduce ringing and overshoot, as shown in the difference

between Figures 35 and 36.

10

9

8

7

6

5

4

3

2

1

0

10pF

100pF

1nF

10nF

CLOAD

Figure 37. Unity Gain Bandwidth vs. CLOAD

Total Harmonic Distortion and Crosstalk

The OPx62 device family offers low total harmonic distortion.

This makes it an excellent device choice for audio applications.

Figure 38 shows a graph of THD plus noise figures at 0.001%

for the OP462.

Figure 39 shows a graph of the worst case crosstalk between two

amplifiers in the OP462 device. A 1 V rms signal is applied to

one amplifier while measuring the output of an adjacent ampli-

fier. Both amplifiers are configured for unity gain and supplied

with ± 2.5 V.

REV. C

–11–

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