Analog Circuit Design

2

Minimizing switching regulator residue in linear regulator outputsBanishing those accursed spikes

Jim Williams

Introduction

Linear regulators are commonly employed to post-regulate switching regulator outputs. Benefits include improved stability, accuracy, transient response and lowered output impedance. Ideally, these performance gains would be accompanied by markedly reduced switching regulator generated ripple and spikes. In practice, all linear regulators encounter some difficulty with ripple and spikes, particularly as frequency rises. This effect is magnified at small regulator V_IN to V_OUT differential voltages; unfortunate, because such small differentials are desirable to maintain efficiency. Figure 2.1 shows a conceptual linear regulator ...