Friday, May 27, 2011

Mini Mic Pre-Amplifier Circuit based IC LM358

The following diagram is a easy to build, simple and low cost mic pre-amp circuit which build using op-amp chip of LM358.
Mini Mic Pre-Amplifier Circuit based IC LM358

Component Parts List:
R1, R3, R4 = 10K
R2 = 1K
R5 = 100K-1M Potensiometer
C1 = 0.1uF
C2 = 4.7uF/16V
IC1 = LM358 dual op-amplifier
Mic = Electret Microphone


  • Vary the variable resistor of R5 to adjust the gain of op-amplifier IC LM358.
  • The LM358 has two op-amp module, you may build stereo audio pre-amplifier using single LM358.

Need a reference for LM358? Then download LM358 datasheet

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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