Transistor Headphone Amplifier

Here is a low-cost stereo amplifier for driving low-impedance headphone devices. The circuit is shown in the attached figure. The circuit uses several commonly used transistors (BC547, BC557) and passive components such as resistors, diodes and capacitors. In order to drive the headphones, the circuit uses a first-stage preamplifier and a push-pull circuit composed of NPN and PNP.

The stereo preamplifier is composed of transistors T1 and T6. They are used to supply input signals for the left and right channels respectively. The amplified left channel input signal is fed into the push-pull stage composed of transistors T2 and T3 to drive the left channel headphone. Similarly, the amplified right channel input signal is fed into the push-pull stage composed of transistors T4 and T5 to drive the right channel headphone.

When the circuit is powered by +6V to +12V, its output voltage can reach 100 to 200mV. Due to the low power consumption of the circuit, it can also be powered by a +9V PP3 battery.

Install the circuit on a PCB and put it into a suitable small box. Stereo headphones can be purchased from the electronics market.

Components should be carefully soldered on the PCB to avoid cold soldering. After the circuit is installed and soldered, a +9V PP3 battery can be used, and the circuit is now ready for use. In the case of AC power, any common voltage regulator (+6~+12v100mA) can be used to power the circuit.