The prominent challenges faced by audio amplification designers’ are power consumption and noise filtration. One way to meet these requirements is by using JFET input operational amplifiers. This circuit is built around TL071, a JFET input op-amp IC. JFET’s input biasing current is almost negligible, resulting in a very low current noise. The low noise, low power consumption, and low Total Harmonic Distortion (THD) make TL071 an excellent choice to be used in the pre-amplification phase.
This circuit operates with a voltage range of 9 to 12 Volts, hence enabling it to be used on a single battery-operated device. Replacing an electret microphone with another audio source can be used for the pre-amplification of instrument sounds, audio mixing desks, and sound cards.
Hardware Components
The following components are required to make the Microphone Preamplifier Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Op-amp IC | TL071 | 1 |
| 2. | Resistors | 62KΩ, 10KΩ | 2, 2 |
| 3. | Capacitors | 47μF, 10μF, 1μF | 1, 2, 1 |
| 4. | Power Supply | ± 12V | 1 |
| 5. | Electret Microphone | – | 1 |
| 6. | Breadboard | – | 1 |
| 7. | Connecting Wires | – |
TL071 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of TL071
Microphone Preamplifier Circuit
Working Principle
The microphone is biased using the 10k ohm resistor; the range of this resistor depends on the supply voltage, operating voltage, and current of the microphone. As, the 1uF capacitor impedance is very less than the 10k ohm resistance, therefore the AC current will flow towards the Op-amp. Moreover, the 1uF capacitor will only allow the AC component of the microphone to pass, blocking the DC component.
At the output of TL071 IC, there will be amplified AC voltages, along with 4.5Volts DC in case of a 9V power supply, and 6 Volts in case of a 12V power supply. The amplified AC voltages can be regulated by installing a potentiometer at negative feedback of OP-amp. Finally, the 10uF capacitor will only pass AC voltages to be collected at audio out.
Applications
- Audio recording: Due to its low noise, this circuit can be used as an excellent choice for an audio recording pre-amplification.
- Sound cards: The circuit can be operated by a single source battery, making it a perfect fit for electronic sound cards.
- Instruments pre-amplification: Various music instruments can utilize this circuit for low noise pre-amplification.
- An important part of a pre-amplification stage of Oscilloscope, Live music, and DJ mixers.
