LMC6484 Datasheet, PDF (27/45 Pages) National Semiconductor (TI) – CMOS Quad Rail-to-Rail Input and Output Operational Amplifier

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Typical Application (continued)
LMC6484
SNOS675C – AUGUST 2000 – REVISED SEPTEMBER 2015
Figure 51. LMC6484 Noninverting Amplifier, Compensated to Handle a 330-pF Capacitive Load
R1 and C1 serve to counteract the loss of phase margin by feeding forward the high-frequency component of the
output signal back to the inverting input of the amplifier, thereby preserving phase margin in the overall feedback
loop. The values of R1 and C1 are experimentally determined for the desired pulse response. The resulting pulse
response can be seen in Figure 52.
Figure 52. Pulse Response of LMC6484 Circuit in Figure 51
8.2.2.2 Compensating for Input Capacitance
It is quite common to use large values of feedback resistance with amplifiers that have ultra-low input current,
like the LMC6484. Large feedback resistors can react with small values of input capacitance due to transducers,
photodiodes, and circuit board parasitics to reduce phase margins.
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