2 transistors Microphone preamplifier


This is a simple microphone preamplifier circuit that use 2 transistors are connected in the direct coupling, to respond the signal even better.

How it works
In Figure 1 the circuit diagram
The circuit

On collector of Q2 will feedback signal to the emitter of Q1, To frequency response is improved.

And,at the same time R1 will connect voltage from the emitter of Q2, to bias Q1.

The input signal into C1 to amplifier by Q1,Q2 and then there are the output signal at collector of Q2 through capacitor-C6 to a power amplifier.

The power supply of the circuit, we may use simple circuit as shown in block dash include Full wave rectifier D1,D2 and capacitor filter C7.

But someone want the high quality power supply should use 12V dc regulator.

The parts you need.
Q1-Q2______.BC548.BC547.BC549____45V 100mA NPN Transistor
R1_________390K___0.25W tolerance: 5%
R2________680 ohms___0.25W___”____
R3________100K_______0.25W___”____
R4,R5_____ 220K_______0.25W___”____
R6________ 10K________0.25W___”____
R7_________ 1K________0.25W___”____
C1________1uF 50V Electrolyte Capacitors
C2,C4_____4.7uF 16V ___”________”____
C3________100pF 50V__”________”____

How to builds
Figure 2 is Actual-size of Single-sided Copper PCB layout and Components layout of this projects.
Actual size of Single sided Copper PCB layout and Components layout


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