Since i installed lateral mosfets in my mosfet citation 12, i am only getting half the power out on the onset of clipping.

With two IRFP450's i get 120W into 1.95 ohms and 100W into 3.9 ohms.

With lateral mosfets i only get 32 watts into 1.95 ohms and 50 watts into 3.9 ohms for the same supply voltage.

Why is this ? Does laterals need a higher drive voltage for a given output voltage ?

There's probably two effects:

- the laterals need higher gate-to-surce voltage which means the drivers hit the rails with the output still apprciably below it;

- the laterals have significant internal resistance meaning that with higher output current (especially in low impedances like your 2 and 4 ohms) you lose significant voltage across the device.

Not sure which effect is dominant here.

You could check the difference in Vgs in the data sheets, that should make it clear.

jan didden