Cross-over distortion can't be simulated?

[James]

When I short D1,D2 of the sample design "Poweramp.dsn",I can't see any cross-over distortion! I've change Q1,Q2 to some SPICE models,the result is the same.
We need to explain it to some customers. Pls help us.

[Richard_Reeves]

You'll not see any cross-over distortion without a load. Without a load, you're not actually using the transistors as current-amplifiers, just moving the emitters up and down. The distortion occurs because in the dead-band where both BJTs are off, no current can be supplied to the load.

If you set the voltage probe to load to ground with 8 Ohms, your distortion will appear, as the transistors are doing some work.

Hope that helps!



Richard

[James]

Thanks a lot!