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Well, that's a subtle variation on a emitter follower double...

Do you have a reference to Hawksford's original article?

Basically it's just an emitter follower driving an emitter follower. The only twist is that the supply voltage on the rail of the first emitter follower is modulated by the audio signal. This only affects the operation of the circuit via the Early effect, whereby the collector current is very slightly dependent upon the collector-emitter voltage.

In a conventional emitter follower the Early effect comes into play, since the collector voltage is constant while the emitter voltage has the audio signal impressed upon it. In this circuit, the second emitter follower is essentially keeping the C-E voltage constant across the first emitter follower via a bootstrap operation.

The only other thing to note is that the two transistors are complementary. This should tend to slightly reduce the even-order distortion compared to a pair of same-sex devices.

Not a bad circuit, but certainly not a fundamentally different circuit than a normal pair of emitter followers (and also not an "inside-out Sziklai")

Thanks,
Charles Hansen

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