I've built a AB class mosfet output amp using two pairs of IRF640/9640 as output devices.
The strange thing is that the amp has worked, and suddenly it stopped working and smoke appeared in the output mosfets, and they didn't had any shortcircuit beetwen GS or DS or GD!
What can be happening, and how can I solve it.
PS: I have built this amplifier before but with less power and only one pair at the output something like three weeks ago, and it is working fine, the only changes are some different resistor values the aditional pair and some zener protection diodes.
Need lots of help.
The strange thing is that the amp has worked, and suddenly it stopped working and smoke appeared in the output mosfets, and they didn't had any shortcircuit beetwen GS or DS or GD!
What can be happening, and how can I solve it.
PS: I have built this amplifier before but with less power and only one pair at the output something like three weeks ago, and it is working fine, the only changes are some different resistor values the aditional pair and some zener protection diodes.
Need lots of help.