John Larkin wrote:
On Wed, 17 Nov 2004 22:49:08 GMT, "Karl Uppiano"
wrote:

We're taking a flawed design, and adding band-aids on top of
band-aids. You can make a perfectly good amplifier with one opamp
and two push-pull emitter followers biased with a couple of diodes,
similar to the first design sketched in the OP's link. If that
design draws too much idle current, increase the emitter resistor.
There's lots of stuff you can do to improve that design without
resorting to the demented design being proposed.


It's actually not a bad idea to have an opamp per output transistor,
if you do it right, which this guy clearly hasn't. I make a power amp
that uses 32 300-watt fets in the output (16 p-ch, 16 n-ch, +-200 volt
rails) and do just that.

Bloody hell. That's some amp, probably about 20KW out. This will
certainly kick the **** out of you at 50 Hz.

How did you get the opamp voltage rating, or was it a discrete one?

It forces essentially perfect current
sharing, nukes the device tc and part-part variations, and makes lots
of gate drive available.

So long as the loop is stable its ok.

Kevin Aylward

http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.