Microphones can hear sound but the signal is very weak.
Then this Simple MIC Amplifier Circuit using IC LM358 make signal strong.
LM358 chip is cheap, easy and can work with two mic signals so people use it a lot.
Audio amplifiers take weak sound signals from mic or music player and make them strong to hear in speaker or headphone.
Circuit Working:
Parts List:
| Category | Item | Quantity |
|---|---|---|
| Resistors | 10k 1/4 watt | 3 |
| 680Ω 1/4 watt | 1 | |
| Potentiometer 100k | 1 | |
| Capacitors | Electrolytic 1μF 25V | 1 |
| Electrolytic 10μF 25V | 1 | |
| Semiconductors | IC LM358 | 1 |
| Electret MIC | 1 | |
| 8Ω speaker | 1 |
LM358 is special chip used in this circuit.
It has two small amplifiers op-amps inside and works with one power source and is so very good.
We can use one or both op-amps which depends how strong signal we want.
It works with voltage from 3V to 32V we can refer to datasheet for more information.
Circuit uses condenser mic which is cheap and popular mic.
Mic change sound to electric signal.
It works like small capacitor with sound hit thin plate, it vibrate, change capacitance and make signal.
This circuit use only one op-amp from LM358 and it is set as inverting amp with negative feedback.
Mic get steady power from voltage divider.
Resistor R1 control where audio signal enter and mic current.
Capacitor C1 let signal go through resistor R2 before it goes to amp.
Boosted signal goes to 8 ohm speaker at the end.
Formulas:
Using LM358 op-amp we can make mic amplifier with this basic formula:
Resistors:
Need resistors to set amplifier gain.
For non-inverting amp gain (G) is:
G = 1 + Rf / Rin
where
- Rf is the feedback resistor
- Rin is the input resistor which connects to mic
How to Find Gain:
Decide how much gain (G) we want.
Choose Rf and Rin to get that gain.
Note:
Use LM358 to build good mic amp by following this above steps.
Change resistor values to fit our needs.
How to Build:
To build a Simple MIC Amplifier using IC LM358 we need to follow the below connections steps:
- Gather all parts same as circuit diagram above.
- Pin 1 of LM358 goes to ground through capacitor C2 and 8 ohm speaker.
- Pin 2 goes to middle leg of VR1 and also connect R3 and C1 to pin 2.
- Pin 3 connect between resistors R3 and R4.
- Pin 4 goes to ground.
- Pin 8 goes to +5V to +9V power.
- Connect resistor R1 and electret mic from power to ground.
Conclusion:
This Simple MIC Amplifier Circuit using IC LM358 makes mic signal strong for speaker.
We can use both op-amps for more gain or only one for less power.
Always follow safety while making circuit.