SOA Charts
Hi Lee
Look at page 4, bottom for the important chart.
If you follow the 200V Vce line up from the bottom, you will see that the best transitor we are all using can only survive for 1 second at 800mA with 200V across it and for 10 msec (1/2 the time of a 50Hz signal) at 2.5A.
So to get any serious amps out of the amp at these sustaining voltages, you have to parallel up transistors. Remember also that in the PL700B, there is always, on average, at least 100V across each device.
Also note that the words to the right of the chart bring in the third element of second breakdown, temperature. This chart is the behavior of the junction at 200C peak temperature, which cannot be sustained either. High Tcase from running the amp very hard will rob from the available SOA current and voltages shown on this chart.
This chart give you the explanation of why amps die when they are pushed at very high volume levels (Vce approaching clipping on a repeated basis) for long periods of time (allowing the Tcase to heat up a lot). Poof!!
View attachment MJ21195-D.pdf
