The following is a 60 - 90W High Quality power amplifier.
Circuit topology is about the same of the above mentioned amplifier,
but the extremely IRFP9240 Rugged IRFP240 MOSFET devices and are used
as the output pair, and well Renowned high voltage Motorola's
transistors are employed in the preceding stages. The supply rails
prudentially voltage was kept at the rather low value of + and - 40V.
For those wishing to experiment, the supply voltage rails could be
raised to + and - 50V maximum, allowing the amplifier to approach the
100W into 8 Ohm target
Note:
- A small, U-shaped heatsink must be fitted to Q6 & Q7.
- Q8 & Q9 must be mounted on large heatsinks.
- Quiescent current can be measured by means of an Avo-meter wired in series to the positive supply rail and no input signal.
- Set the Trimmer R10 to its minimum resistance.
- Power-on the amplifier and adjust R10 to read a current drawing of about 120 - 130mA.
- Wait about 15 minutes, watch if the current is varying and readjust if necessary.
List Component:
R1______________47K 1/4W Resistor
R2_______________4K7 1/4W Resistor
R3______________22K 1/4W Resistor
R4_______________1K 1/4W Resistor
R5,R12,R13_____330R 1/4W Resistors
R6_______________1K5 1/4W Resistor
R7______________15K 1/4W Resistor
R8______________33K 1/4W Resistor
R9_____________150K 1/4W Resistor
R10____________500R 1/2W Trimmer Cermet
R11_____________39R 1/4W Resistor
R14,R15___________R33 2.5W Resistors
R16_____________10R 2.5W Resistor
R17_______________R22 5W Resistor (wirewound)
C1_____________470nF 63V Polyester Capacitor
C2_____________470pF 63V Polystyrene or ceramic Capacitor
C3______________47µF 63V Electrolytic Capacitor
C4,C8,C9,C11___100nF 63V Polyester Capacitors
C5______________10pF 63V Polystyrene or ceramic Capacitor
C6_______________1µF 63V Polyester Capacitor
C7,C10_________100µF 63V Electrolytic Capacitors
D1___________1N4002 100V 1A Diode
D2_____________5mm. Red LED
Q1,Q2,Q4_____MPSA43 200V 500mA NPN Transistors
Q3,Q5________BC546 65V 100mA NPN Transistors
Q6___________MJE340 200V 500mA NPN Transistor
Q7___________MJE350 200V 500mA PNP Transistor
Q8___________IRFP240 200V 20A N-Channel Hexfet Transistor
Q9___________IRFP9240 200V 12A P-Channel Hexfet Transistor
