Transistor Amplifier 400mW

The small amplifier consists of 3 transistors and passive components. It can deliver 400mW power at 9VDC operating voltage, speaker impedance is 8-OHM. The input signal is between 200mV and 2V. The quiescent current is adjusted with the R10 50K trimpot.

When the amplifier is idle (without a speaker connected and input signal) the current on the R7, R8 resistors should be between 5…10mA with 9VDC input voltage

400 mW Amplifier Specifications

Distortion factor: <0.4% Signal-to-noise ratio: >75 dB
Power bandwidth: 40 Hz – 600 kHz
Operating voltage: 8VDC – 12VDC

400mW Amplifier Parts List

RESISTANTS:
R7, R8: 1-OHM
R5, R6, R9: 470-OHM
R2: 10K
R4: 15K
R3: 56K
PT1: 10K TRIMPOT. (VOLUME)
PT2: 50k TRIMPOT.
CAPACITORS:
C2, C3: 22pF
Cl, C4: 220UF 16V
SEMICONDUCTORS:
T2: BC337
T3: BC327
T1: BC548C
D1, D2: 1N4148

Source: de.elv.com/p/400-mw-transistor-verstaerker-P202901/