Wide bandwidth class AB with 10mA quiescent?

[newvirus2008]

We can easily spend a decade for further simulations; what I suggest is that you try out this circuit in real world--of course first just with low-voltage power supplies. This will teach you much more. How close are the bias conditions to what your simulator tells you? Is the circuit indeed stable, or did SPICE miss some parasitic oscillation? Is the predicted distortion performance anything close to the measurement result? Is the DC offset acceptable, or did it suddenly became much larger than in SPICE world?

Samuel

Sir, I completely agree. Its been days doing the fantasy thing. I really want to know whether it is "workable" or not.

Meanhile I ve again spiced up a similar circuit for 360Vpp output. BJT s are FZT458 /558 (except driver 2scw3601/2sa1407)

 

[godfrey]

Meanhile I ve again spiced up a similar circuit for 360Vpp output.

Don't you need thermal compensation? IMO the mosfet's current will rise rapidly with temperature.

 

[newvirus2008]

Don't you need thermal compensation? IMO the mosfet's current will rise rapidly with temperature.

The gate bias for the MOSFETs are proportional to the Vbe(on) of BJTs. I suppose, if a tight thermal coupling (metallic plate etc.) is arranged for the whole module, then the thermal feedback loop may considered to be already built in.

I am not very sure of the practical consequences. But will arrange for a current limit to rule out any catastrophic events (like SOA violation etc)

 

[newvirus2008]

I have made a board for low voltage (+/-30V) and the bias voltages are fairly accurate.
Output is pulled to +/- rail (open-loop with inputs shorted together). Mosfets 610/9610.
Seem to conduct more current than the spice model.

 

[newvirus2008]

The 30V amplifier is stable and working on a general purpose PCB but it doesnt seem to have good slewrate.
It can do 60Vpp at 200k and 50Vpp at 400k. All transistors are BC546/556. Is it because of these small transistors that the slewrate is limited? DC offset in closed loop condition is 200mV.


I havent got all components required for the actual high voltage version.