The normal condensor MIC needs a good pre amplifier circuit for boosting the small audio signal coming from the MIc. So in this article i’m sharing a simple MIC preamp circuit using 2N3904 NPN transistor. This entire circuit is working with a 9V battery, you can use normal 9V battery to power the circuit. The pre amp circuit is amplifies the weak microphone signals and in output section. The amplified output signal can be used for further amplification using big audio amplifiers.
2N3904 Pinout
| Pin Number | Pin Name | Description |
|---|---|---|
| 1 | Emitter | Current flows out to ground |
| 2 | Base | Controls current flow between collector and emitter |
| 3 | Collector | Current flows in from the load |
Components Required
| Component | Value / Part Number | Quantity |
|---|---|---|
| MIC | Condenser MIC | 1 |
| R1 | 1kฮฉ | 1 |
| R2 | 100kฮฉ | 1 |
| R3 | 10kฮฉ | 1 |
| R4 | 27kฮฉ | 1 |
| U1 | 10ยตF / 16V | 1 |
| U5 | 10ยตF / 16V | 1 |
| Q1 | 2N3904 | 1 |
| SWITCH | SPST | 1 |
| DC Supply | 9V Battery or DC Adapter | 1 |
Circuit Diagram
Construction and Working
A condensor MIC is connected to the circuit which is the main electronic component for capturing the external audio signals. 27K ohms of biasing resistor is connected with the MIC to power it. a 10uf coupling capacitor is also connected with the MIC to blocking the DC voltage and allowing AC voltage passe to the base of 2N3904 transistor.
The 2N3094 NPN transistor is acts as a common emitter amplifier to amplifying the weak audio signals comes from the condenser mic. A 10uf capacitor is also using between the audio output for removes any DC offset from the amplified signal and it allows to pass a clean AC audio signal in output.
