Thursday, June 16, 2011

18W Audio Amplifier Circuit based TIP41A/TIP42A

This is an amplifier circuit capable to deliver 18 Watt RMS into 8 Ohm speaker. You do not need to build a preamplifier because the pre-amp already included in the this circuit based IC TLE2141C which is a low noise, high voltage, high slew-rate Op-amp.

18W Audio Amplifier Circuit based TIP41A/TIP42A

Amplifier parts list:
P1 = 22K Log. Potentiometer (Dual-gang for stereo)
R1 = 1K
R2 = 4K7
R3 = 100R
R4 = 4K7
R5 = 82K
R6 = 10R 1/2 watt
R7 = R22 4W Resistor (wirewound)
R8 = 1K 1/2W Trimmer Cermet (optional)
C1 = 470nF
C2,C5 = 100µF/3V Tantalum
C3,C4 = 470µF/25V
C6 = 100nF
D1 = 1N4148
IC1 = TLE2141C
Q1 = BC182
Q2 = BC212
Q3 = TIP42A
Q4 = TIP41A

Power supply parts list
R9 = 2K2 1/4W Resistor
C7,C8 = 4700µF 25V Electrolytic Capacitors
D2 = 100V 4A Diode bridge
D3 = 5mm. Red LED
T1 = 220V Primary, 15 + 15V Secondary, 50VA Mains transformer

18W Audio Amplifier Circuit Notes:

  • Can be directly connected to CD players, tuners and tape recorders.
  • Do not exceed 23 + 23V supply.
  • Q3 and Q4 must be mounted on heatsink.
  • D1 must be in thermal contact with Q1.
  • Quiescent current (best measured with an multimeter in series with Q3 Emitter) is not critical.
  • Adjust R3 to read a current between 20 to 30 mA with no input signal.
  • To facilitate quiescent current setting add R8 (optional).
  • A correct grounding is very important to eliminate hum and ground loops. Connect to the same point the ground sides of J1, P1, C2, C3 & C4. Connect C6 to the output ground.
  • Then connect separately the input and output grounds to the power supply ground.


About Audio Amplifier
An audio amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 - 20 000 Hz, the human range of hearing) to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain.

The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification, equalization, tone control, mixing/effects, or audio sources like record players, CD players, and cassette players. Most audio amplifiers require these low-level inputs to adhere to line levels.

While the input signal to an audio amplifier may measure only a few hundred microwatts, its output may be tens, hundreds, or thousands of watts. More explanation about power audio amplifier can be found at

This is a video tutorial about how to a very simple audio amplifier based on the LM386 amplifier chip. It can be built for less than $20 (or might be less than $8 in some countries) and used to amplify any low level audio signal including a guitar, bass or mp3 player.

Watch the video:

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