The Design of Active Crossovers, 2nd Edition

Chapter 16

Opamps for Active Crossovers

Active Devices for Active Crossovers

It is a truth universally acknowledged, that if you are designing an active crossover, you will need active devices. In this day and age that almost always means opamps. Active crossovers can be built with discrete transistor circuitry if this is desirable for performance benefits or marketing reasons. This is relatively straightforward for Sallen & Key filters that require only a unity-gain buffer or voltage-follower, which can be implemented as some form of emitter-follower. It is a bit more complex for MFB filters and some equaliser circuits, which require a high-open-loop-gain inverting amplifier, and more complex again for configurations such as state-variable filters, ...