LMP7717, LMP7718

SNOSAY7H – MARCH 2007 – REVISED MARCH 2013

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Figure 53. RC = 240Ω and C = 390 pF, Gain = −1

Figure 54. RC = 240Ω and C = 2.2 nF, Gain = −1

To summarize, the following steps were taken to compensate the LMP7717 for a gain of

−1:

1. Values for Rc and C were calculated from the Bode plot to give an expected phase margin of 45°. The values

were based on RIN = RF = 2 kΩ. These calculations gave Rc = 330Ω and C = 390 pF.

2. To reduce the ringing C was increased to 2.2 nF which moved the pole of F, the feedback factor, farther

away from the AVOL curve.

3. There was still too much ringing so 2 dB of over-compensation was added to F. This was done by

decreasing RC to 240Ω.

The LMP7715 is the fully compensated part which is comparable to the LMP7717. Using the LMP7715 in the

same setup, but removing the compensation network, provided the response shown in Figure 55 .

Figure 55. LMP7715 Response

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