VSXD 938TX is a Multichannel Receiver produced by PIONEER at last 90s and famous in 2000s and it uses MOSFET as final power components.
Its consist of 4 power amplifier inside the unit for making audio surround system.
SCHEMATIC DIAGRAM
The amplifier using symmetrical 42VDC to supplying the circuit. With use only 1 pair of MOSFET, it can deliver 100 Watts output audio at 8 Ohm Load.
With 42VDC, its possible to make 150 Watts audio at 4 Ohm load. But its not recommended for connect below 8 Ohm load because its only using 1 pair of MOSFET that only 107 Watts of dissipation.
In the preamplifier block, needs 5 transistors Q501 to Q505 to get stable and even audio results.
While Q506 and Q507 served as voltage amplifier transistors.
Q2502 is a servo driver transistor and its located same with the power transistor heatsink.
The function of trimpot VR2501 is to determine the current ambient of the MOSFET to start conduct the current.
Q508 and Q509 are driver transistors.
And finally the MOSFET Q510 and Q511 as the final amplifier.
The IRF540 MOSFET able to deliver until 28 Amp of current and producing up to 107 Watts of power dissipation
( DATASHEETS ) .
