7W Audio Power Amplifier LF356

As shown for the low-frequency output 7W power amplifier circuit. The circuit uses a FET input type operational amplifier LF356 integrated as a voltage amplification. The class
7W Audio Power Amplifier LF356 - schematic

as a transistor amplifier circuit composed of the driver stage. Illustrated circuit has adopted a large negative feedback loop, which feedback resistor R2 is 100k, input terminus C1 (1 F) and R1 (10k ) constituting the coupling circuit. The AC component of the input signal is applied to the op amps inverting input (pin 2), the voltage can be seen, the circuit magnification: Av -R2/R1 -100/10 -10. Stage amplifier circuit composed of complementary symmetry circuit by the transistor, the transistor connected to form a composite tube, transistor VT1 and VT2 can be 2SC1815, VT5 and VT4 can be used 2SA105, VT3 selection 2SD525, VT6 use 2SB595, after the amp has an overcurrent protection circuit If amplifier tube VT3 (or VT6) output current is too large, then the emitter 0.5 resistor R7 (or R8) will have a greater voltage drop, its polarity is positive on the negative. The voltage applied to VT1 (or VT4) between the base and emitter, so VT1 (or VT4) positively biased conduction (when the external load short-circuit, the saturated conduction), VT1 to VT2 conduction from diversion effect, make VT2 (or VT5) base current decline, thus limiting the VT3 (or VT6) of output current to prevent it from being damaged due to excessive current. Due to the large VT3 and VT6 power, you need to install the radiator.

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