Microphone Amplifier

If you are looking for the sensitive sound pick-up circuit then here is exactly what you are looking for. The circuit given in this site can be used as a different devices. It can be used as a simple microphone as well as with more exotic device as a sound operated alarm. This circuit is equally effective for a bugging device.



R11.2 KΩ
R22.7 KΩ
R333 KΩ
R46.8 KΩ
R53.3 KΩ
R7560 KΩ
R84.7 KΩ
R910 KΩ
C147μ  10V
C4220μ  10V
BATT 6VOLT Battery
MICCondenser Microphone
OTHERsPCB ,Connecting  wires, hardware etc...


Circuit Diagram


Microphone Amplifier Circuit



Circuit Description

Microphone Amplifier
Microphone Amplifier

Here in the circuit diagram you can see that microphone is employs as the transducer. The output of the condenser microphone is quite low it has to connect with an FET amplifier. This amplifier circuit is power by the R1,R2 resistor network. The output of condenser microphone is fed to a two-stage amplifier. Transistor T1 (BC149C) utilise current series feedback the first stage. The second stage comprising transistor T2 is connected in the voltage shunt feedback configuration. These two stages provide sufficient gain to pick up even the slightest whisper. The amplifier circuit in the site requires  4.2 volt supply which can be obtained with a resistor R9 [1k]. The value of this resistor may be altered to suit a supply voltage other than 6 volts. Output of the microphone amplifier can be made variable by connecting a 10k potentiometer as shown in the circuit. Circuit‘s gain can be increased by reducing the value of R6 to 47 ohms or 22 ohms. depending on the input sensitivity of the main amplifier system. Increase in gain was also observed by using 3V supply and eliminating R9 altogether. The microphone should be housed in a small round enclosure.

5 thoughts on “Microphone Amplifier”

  1. Hi Krishan

    I am trying to make a push to talk microphone circuit for an external microphone on a hand held radio. Can the above be modified to suit this purpose.

    thanks for your time


  2. I am looking to use this or something similar to make a led light when the mic pics up sound. 5he form factor is important need to hide board in a power wheel toy and wire it for lights. How big is the board and coukd I extend the distance of the mic location with out compromise of pick up ability. Also is this avaliable to buy completed.

  3. It is anice simple circuit. Iwant to connect now to make ‘Hearing Aid’.
    If you have any circuit using Fet IC eg. TLO 72, pl.inform me. Thanks.

  4. It is a nice simple circuit. I want to connect now to make ‘Hearing Aid’.
    If you have any circuit using Fet IC eg. TLO 72, pl.inform me. Thanks.
    Regards. ( Small Corrections made)

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