# 555 timer IC audio amplifier circuit schematics

Here we are going to discuss about a simple timer IC 555 project. The 555 timer IC can be used as an audio amplifier with astable multivibrator configuration. It functions as to carry out pulse width modulation (PWM) of audio signal. Current(I) capacity of 555 timer amplifier is 200mA which is sufficient to drive a small speaker. This simple 555 IC based amplifier circuit is a good substitute for conventional low power amplifiers. The low frequency audio signal is applied to the control voltage pin (5th pin) of 555 for pulse width modulation (PWM) generation. For beginners who want to know ‘what is PWM?’, read simple PWM modulation concept.

## Circuit diagram of 555 amplifier

Click on the image for enlarged view

## Components required

1. Power supply
2. Resistors (1kΩ x 2; 10kΩ; 47kΩ; 100kΩ; 680kΩ)
3. Capacitors (10pF; 0.1µF, 1µF, 10µF x 2)
4. Transistor (BC547)
5. Timer IC 555
6. Condenser mic
7. Loudspeaker (8Ω)

## Working Principle

• In the normal mode, we just open circuit the 5th pin (Control voltage pin) of 555 IC. But the most interesting fact we often neglect is that if a low frequency signal is applied to the 5th pin of 555 IC, pulse width modulation starts.
• Here the oscillating frequency of 555 astable is approximately 145 KHz. The discharge time of capacitor C3 via diode 1N4007 is too fast since there is no resistor to discharge.
• The condenser MIC is used as transducer to sense the incoming audio signals and convert them to proper electrical signals.
• The output of the MIC is then fed to the transistor Q1 via a capacitor C1. This capacitor is used to remove the DC component of the signal.
• Resistor R1 provides the necessary biasing to the condenser microphone. And the resistors R2 and R3 gives potential divider bias to BC547 transistor.
• The capacitor C2 and resistor R4 provides negative feedback to the transistor circuit which is essential for amplification.
• The pre amplified audio signal is fed to the control voltage pin of 555 timer astable multivibrator running with 145kHz.
• The process of pulse width modulation starts and as we know the speaker does not respond to this much high frequency, it responses to the usual DC value of the modulated output. Hence the audio signal gets amplified.

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## 12 thoughts on “555 timer IC audio amplifier circuit schematics”

1. Jackson Mgani says:

i like u’r designs but I need a help in PIC programming can u do it for me.

2. Jackson Mgani says:

I like u’r good design but can u help simp PIC with c language project just input and output.

• Jaseem vp says:

Hi Jackson Mgani,
We had posted many PIC Microcontroller series, it includes Getting started guide to Engineering projects. Please checkout our PIC Microcontroller category

3. andrea says:

what is the wattage of each resistors found in this circuit? Please answer. Thanks. 🙂 i need it for my school project

4. Ali says:

hello,is the cond mic, the same as the normal mic typically used.thank you.

5. Paul says:

The +ve of C5 should be connected to Vcc 5v not the loudspeaker.

6. gowtham says:

sir pls tell me whether the output for this circuit is coming or not if coming pls send me the pcb layout for this circuit diagram

7. Ugochukwu says:

I tried the circuit but it’s not working. What could I have gotten wrong?

8. surendra says:

hi…. can you provide me what is the output power(in watts)?
and what is the perfection of sound is there any noise?….thank u

9. capsolyne says:

it’s not working 🙁

10. MS SUNIL KUMAR says:

HI SIR, THIS IS SUNIL. PLEASE SEND AUDIO AMPLIER CIRCUIT WITH ONE OUTPUT SPEAKER. ANOTHER ONE LED AND OTHER ONE MOTOR.PLEASE SEND ME CIRCUIT TO MY MAIL ID.

11. prajval says:

sir my name is prajwal plz send 3.5v 555ic amplifier ckt my e mail id