Question about Class AB output stage

ian field

Joined Oct 27, 2012
6,539
Hi,

The figure attached shows a class AB output stage. From this circuit can be derived the equation

IN x IP = IQ^2

From this equation it is correct to state that the transistor will never cut off?

Thanks
Most people don't do it that way, mostly because of temperature coefficients.

Generally, you'd use a self compensating arrangement with low value emitter resistors.

diodes of the same semiconductor material, preferably clamped to the same heatsink can be used to provide the reference Vbe for each transistor. You can vary the diode bias current for a bit of wiggle room to clean up any lingering crossover distortion.
 

Thread Starter

Daniel Pereira Carvalho

Joined Oct 10, 2016
2
Most people don't do it that way, mostly because of temperature coefficients.

Generally, you'd use a self compensating arrangement with low value emitter resistors.

diodes of the same semiconductor material, preferably clamped to the same heatsink can be used to provide the reference Vbe for each transistor. You can vary the diode bias current for a bit of wiggle room to clean up any lingering crossover distortion.
Hi Ian,

Thanks for the anwser.

I'm aware that this circuit is can't be used in real devices. I'm using it to simplify the operation analysis.
 
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