Objective of compensation is to achieve stable operation when negative feedback is applied around the op amp. Miller - Use of a capacitor feeding back around a high-gain, inverting stage. Miller capacitor only Miller capacitor with an unity-gain buffer to block the forward path through the compensation capacitor. Can eliminate the RHP zero.
It is observed that as the size of the compensation capacitor is increased, the low-frequency pole location ω1 decreases in frequency, and the high-frequency pole ω2 increases in frequency. The poles appear to “split” in frequency.
When selecting standard value compensating capacitors the next larger values should be used. This is termed over-compensation and it results in better amplifier stability, but, it also produces a smaller circuit bandwidth. Miller effect involves connecting a capacitor between the output and input terminals of an inverting amplifier.
The Miller effect refers to the increase in equivalent capacitance that occurs when a capacitor is connected from the input to the output of an amplifier with large negative gain. This concept is illustrated in Figure 6 for the capacitance case. (a) (b) Figure 6. Illustrating the Miller effect for capacitance.
In addition, a better understanding of the internals of the op amp is achieved. The minor-loop feedback path created by the compensation capacitor (or the compensation network) allows the frequency response of the op-amp transfer function to be easily shaped.
The capacitance on the output is often neglected since it sees and amplifier outputs are typically low impedance. However if the amplifier has a high impedance output, such as if a gain stage is also the output stage, then this RC can have a significant impact on the performance of the amplifier.