Data Sheet

ADA4620-1, ADA4620-2

analog.com

Rev. 0

44 of 49

Figure 132. 100 kHz Third-Order Butterworth Filter Frequency Response

Large Signal Behavior

The ADA4620 is a precision low noise op amp optimized for small signal applications. In the presence of large-signal

fast input steps, it does exhibit some less ideal behaviors. For fast steps much larger than 4 V noninverting, and 8 V

inverting, the output begins to exhibit some delay. This occurs on the rising edge of the input, in either inverting or

noninverting cases. Figure 133 shows the issue in a gain of −1. The test setup involves a supply voltage of ±18 V and

up to ±16 V input. The output delay time starts out at tens of nanoseconds but can be as high as 500 ns for very

large steps. In the noninverting case, shown in Figure 134, steps larger than about 15 V begin to show an extended

overshoot on the output, with amplitude 1.4 V, and output delay times extending into the low microseconds. Figure

133 and Figure 134 show the behaviors all the way up to a 32 V step. In these two figures, the dashed lines represent

the input step signal, and the solid line that overlays the flat portion of each dotted line is the corresponding output

for that input signal.

Figure 133. Large Signal Inverting Output Behavior, Without Feedback C, Input Signals Shown Inverted

MAGNITUDE

PHASE

FREQUENCY (kHz)

1

10

100

500

–40

–35

–30

–25

–20

–15

–10

–5

0

5

–240

–210

–180

–150

–120

–90

–60

–30

0

30

AV = –1

INPUT PULSES ARE DASHED LINES

OUTPUT PULSES ARE SOLID LINES

TIME (1µs/DIV)