Darlington VAS

Let's get back some of the open loop gain that was lost by the increased input stage emitter degeneration. We can add an Emitter Follower (Q12) to our Voltage Amplification Stage (VAS), thus increasing the beta. As the Emitter Follower is inside the C1 loop there is little chance that it will add additional phase shift that could cause global loop stability to suffer (from the Audio Power Amplifier Design Handbook, Douglas Self, ISBN: 0 7506 56360).

gschem Screenshot