Categories: Linear Amplifier

65W Power Amplifier using HEXFET

This is a high quality 65W power amplifier circuit based HEXFET IRF9540 and IRF540. The circuit is quite simple for amplifier with good sound quality. The component parts is easy to find at electronic store around your place. It uses split power supply. Q8, Q10, Q11, Q12, Q13 should be mounted on heatsink for thermic stability.

Parts list:

R1-15-16-21-22-17-18 = 1Kohm	R33 = 68ohm 5W	Q1-2 = BC550C
R2 = 47Kohm	R35-36 = 6.8ohm 1W	Q3-4 = BC560C
R3-4 = 10Mohm	TR1 = 1Kohm trimmer	Q5 = BC560C
R5-6-13-14 = 1.2Kohm	TR2 = 1Mohm trimmer	Q6 = BC550C
R7-12 = 47ohm	C1 = 2.2uF 63-100V MKT	Q7-11 = BD140
R8-9-10-11 = 22ohm	C2 = 1nF 100V MKT	Q8-9-10 = BD139
R19 = 82ohm	C3-4 = 2.7nF 100V MKT	Q12 = IRF9540
R20 = 22Kohm	C5 = 330pF ceramic or mylar	Q13 = IRF540
R23-26 = 56ohm	C6-7 = 100uF 16V	F1-2 = Fuse 2.5A Fast
R24 = 2.2Kohm	C8 = 1uF 100V MKT	L1 = see text [2]
R25 = 560ohm	C9-11-12 = 100nF 100V MKT	J1 = 2pin connector 2.54mm step
R27-30 = 150ohm	C10-13 = 470uF 63V
R28-29-31-34 = 15ohm	C14 = 33nF 100V MKT	Q8-10-11-12-13 on Heatsink
R32 = 150ohm 5W	D1-2 = LED RED 3mm [see text] [1]	All the resistors is 1/4W 1% except quote differently

Here the PCB design layout for this 65W power amplifier:

Power supply for 65W power amplifier circuit using HEXFET:

Power Supply output voltages:

+V1=+35V ? ? -V1=-35V +V2=+12V ? ? -V2=-12V +V3=+35V???? -V3=-35V

Power supply parts list:

T1 = 2 x 25VAC ; 3A ; 160VA // 2X15VAC ; 1A ;? 20VA
T2 = 2 x 25VAC ; 3A ; 160VA
BR1-3 = 200V 35A Bridge Rectifier
BR2 = 4 X 1N4002
IC1 = 7812 Regulator
C5-8 = 1000uF/25V
C6-9 = 100nF

C7-10 = 10uF/25V
C15 = 33nF/630V Class X2
C1,C2,C3,C4,C11,C12,C13,C14 = 10000uF/63V
IC2 = 7912 Regulator
F1 = FUSE 2A slow block
S1 = 2X2 switch 10A
JF1 = 3 pole male plug

More explanation about this 65W power amplifier circuit, visit this page

circuit schematic