35W Audio Amplifier based LM391

Amplifier Circuit — Tue, 20 Dec 2011 03:10:09 +0000

35W audio power amplifier circuit based LM391. It needs only few external components to work. With the TR1 we can adjust the bias current to 45mA. Inductor L1 consists of 20 turns of wire thickness of 0.9mm, around the resistor R16.

This is the circuit diagram of a 35W audio amplifier based on LM391. The LM391 is a comprehensive driver to the power transistors. It needs only few external components to work. With the TR1 we can adjust the bias current to 45mA. Inductor L1 consists of 20 turns of wire thickness of 0.9mm, around the resistor R16. The transistors Q3-4 must be placed onto a heatsinks. If you use the Q3-4 with type of TIPxxxx, you can be placed directly onto the board. But if you use packaged transistors TO-3, then it should be connected with short cables to the respective positions of the board.

Parts List

R1,3,5,8,10 = 1Kohm	C1 = 2.2uF 63V	TR1 = 10K Trimmer
R2,7,11 = 100Kohm	C2 = 4.7uF 25V	D1,2 = IN4002
R4,6 = 4.7Kohm	C3,17 = 47uF 63V	IC1 = LM391
R9,12 = 100ohm	C4,8,9 = 1nF 100V MKT	Q1 = BD139
R13 = 47Kohm	C5 = 47nF 100V MKT	Q2 = BD140
R14,15 = 0.15ohm 5W	C6 = 22pF ceramic	Q3 = TIP2955
R16 = 1ohm 2W carbon 5%	C7,11,12,13 = 100nF 100V MKT	Q4 = TIP3055
R17 = 10ohm 1W carbon 5%	C10 = 22pF ceramic	L1 = See text

Bottom (chopper) PCB layout:
35W audio power amplifier circuit based LM391 – bottom pcb layout. The transistors Q3-4 must be placed onto a heatsinks. If you use the Q3-4 with type of TIPxxxx, you can be placed directly onto the board. But if you use packaged transistors TO-3, then it should be connected with short cables to the respective positions of the board.

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Top (component) PCB layout:
35W audio power amplifier circuit based LM391 – top pcb layout. The transistors Q3-4 must be placed onto a heatsinks. If you use the Q3-4 with type of TIPxxxx, you can be placed directly onto the board. But if you use packaged transistors TO-3, then it should be connected with short cables to the respective positions of the board.

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35W Audio Amplifier based LM391