op-amp frequency compensation, the how and the why

When an operational amplifier is used in a negative feedback circuit its frequency response requires `compensation`, a high-frequency rolloff that may be `internal` or `external`. With inadequate compensation the circuit will usually misbehave or even oscillate. This article will explain the reasons for frequency compensation, describe the usual `simple` approach and then show how an `external` type can be fitted with an improved compensation-arrangement. The latter approach results in a circuit that responds far better to large and fast excursions of the input signal.