Low Noise Electret Microphone Circuit

The circuit starts with the electret microphone.

Low noise electret microphone circuit.

The overall voltage gain of this circuit depends on the resistors used at the non inverting input of this ic. This is the best and interesting circuit for the beginner. The single supply microphone pre amplifier amplifies the output signal of an electret capsule microphone to audio line levels. This circuit can be used to all normal microphone for example.

This article describes an compact electret microphone amplifier but you can connect dynamic microphones with low resistance. An op amp is used as a trans impedance amplifier to convert the output current from the microphone in to a signal level voltage. This low noise microphone amplifier is build with mat02 produced by pmi. The amplification can be 20db or 23 5db 10x or 15x selected by s1.

Simulate this circuit schematic created using circuitlab. This electret microphone in particular needs 2 2v of power in order to. Here is two low noise microphone preamplifier circuit. Finally we need one more component a bypass capacitor between the emitter terminal and the ground thus c e.

Which is simple circuit but high quality sound includes devices that are selected very well. One technique would be to use a third wire to ground the shield as the common xlr connector uses 1. This is another a circuit diagram of homemade mic speaker amplifier using lm386. This circuit can be operated by a 9 12v battery.

3 4 low noise characteristics the electret microphone may be mounted a distance from the actual amplifier. Audio signals are received from electret mic and are sent to the ics input. You can connect any audio source in the place of a microphone. The c1 in this circuit is the same capacitor c described in the electret microphone circuit above and its role is to cut off the dc offset of the input signal such that we work out only the ac component of the input signal.

This creates an additional low pass filter for the microphone bias voltage with a cutoff frequency of about 7 hz. The circuit works with 9v so it is good choice for battery operated systems. As stated the microphone needs power in order to operate. Now that we know all the components we are going to use we will go over the circuit schematic for the electret microphone shown below.

Electret condenser microphone amplifier circuit. The output impedance is 70 ω at 23 5 db gain and with r3 220kω the input impedance is 30kω. This mic amplifier is very performant and has a very low noise level. Note that any noise on the power rail is coupled directly through the bias resistor to a high gain audio input.

This is small and powerful for a low power supply. Electret microphones can be inserted in the same box with the amplifier it only need 5 to 10v or 9v battery with a current consumption of just 1 5ma. The longer the microphone leads the more noise that will likely be picked up.