SNOS674G November 1997 – April 2020 LMC6482
The LMC6482 can typically directly drive a 100-pF load with VS = 15 V at unity gain without oscillating. The unity gain follower is the most sensitive configuration. Direct capacitive loading reduces the phase margin of op-amps. The combination of the output impedance of the op-amp and the capacitive load induces phase lag. This results in either an underdamped pulse response or oscillation.
Improved frequency response is achieved by indirectly driving capacitive loads, as shown in Figure 62.
NOTE: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 amplifiers inverting input, 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 is shown in Figure 63.