Ultra-low quiescent current AF power amplifier

This is an audio power amplifier, similar to what is common in transistor radios and other portable audio equipment. This circuit however, has an ultra- low quiescent current of about 250uA, due to a unique bias circuit. I don’t even know of a chip that does that. This circuit also has much higher open-loop gain, due to the bootstrap effect that the circuit provides as a by-product of its operation.

Source: http://discovercircuits.com/Andy/Ultra.pdf (good site)