This audio amplifier design approach employs TMOS Power FETs operating in a complementary common- source configuration. They are biased to cutoff, then turn on very quickly when a signal is applied. The advantage of this approach is that the output stage is very stable from a thermal point of view. U1 is a high slew-rate amp that drives Q3, Q4,and Q6 (operating class AB) providing level transition for the output stage consisting of Q7, QS, Q9,and QlO.

The positive temperature coefficient of the TMOS device enables parallel operation of Q7, QS, and Q9 and provides a higher power complementary device for QlO. These TMOS Power FETs must be driven from a low-source impedance of 100 0, in order to actually obtain high turn-on speeds.

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