Sunday, September 25, 2011

45W Power Audio Amplifier Circuit with HEXFET

45W Power Audio Amplifier Circuit with HEXFET

This is 45W power audio amplifier circuit which built using HEXFET IRF9540 and IRF540. This is a ideal solution for the make a good, low cost power amplifier circuit.

Components List:
R1 = 47K ohmC1-2-6-7 = 100nF 100V MKTQ5-6 = IRF9540
R2-12 = 1K ohmC3-4 = 22uF 25VQ7-8 = IRF540
R3-4 = 3.3K ohmC5 = 220pF styroflexTR1 = 5K ohm trimmer multiturn
R5 = 1.2K ohmC8-9 = 4700uF 63VTR2 = 1K ohm trimmer multiturn
R6 = [1.2K ohm] 820 ohm *See textC10 = 1uF 100V MKTF1-2 = fuse 3A
R7 = 270 ohmD1-2 = 15V 0.5W zenerJ1 = 2pin connector 2.54mm step
R8 = 220 ohmIC1 = LF411orAD711or LF351J2 = 5pin connector 5mm step
R9 = 27K ohmQ1 = BC550C
R10-11 = 22K ohmQ2 = BC560CAll Resistors 1/4W 1% metal film
R13-14-15-16 = 150 ohmQ3-4 = BC547B

The preamplifier and the driver support in a operational amplifier [IC1]. The voltage fall in resistors R5 and TR2/R6, drive the output FET's gates and is proportional with the input signal level. Transistors Q1-2 function as voltage stabilizers in the supply lines, but ensure also the essential voltage fall, because the IC1 it should not they are supplied with voltage bigger ± 18V. The consumption of all types that can be used in the place of IC1, are 2 mA, this it means voltage fall in terminal the R5 and TR2/R6 equal with the 2.4 until 2.6Volts. The current regulation it become from transistors Q3-4 in Wilson connection and the current adjustment of bias it becomes from the multiturn TR1 trimmer.

Detailed information about this 45W power audio amplifier circuit with HEXFET:

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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