[Photo] Amplifier circuit made with LM317

The power amplifiers made with the stable voltage regulator set are of great significance to electronic enthusiasts as an attempt to develop ideas. This circuit is pure Class A work, and low noise tube is used for voltage amplification, so THD, NF and other indicators are good, and the output power can reach 30W


As shown in the circuit, the transistor VT1 acts as a voltage amplifier. Because the input impedance of the voltage-stabilized integrated circuit IC1 is high, its operating current is only 0.6mA. R1 and C3 are power supply decoupling, and C4 is used to prevent parasitic oscillation The R3 and R4 partial voltages provide bias and AC / DC feedback to VT1 to improve linearity and DC stability. VT2, R5, R6 and diode constitute a constant current source, which is used to improve the efficiency and output power of the circuit and increase the output dynamic range.

Because the circuit is particularly simple, the components can be lap welded. The constant current of the constant current source can be set at 10 ~ 15mA. During debugging, the output voltage of the LM317 can be adjusted to half of the power supply voltage. The quiescent current is about a dozen mA. The power of the power transformer T1 shall not be less than 50W.


Three-terminal voltage regulator IC selects LM317, and transistor VT1 selects 9014. VT2 selects 8050 type, diodes VD5 and VD6 select 2CP20, and the power of the transformer should be greater than 50W

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