Microphone amplifier
The microphone amplifier is designed to increase the power of the signal coming from the microphone. As a rule, the power of such a signal is very small and equal to and less than a microwatt unit. And in order to hear the sound in the dynamics will require power already in watts. Therefore, the microphone amplifier should realize amplification thousands of times. Most often, the microphone amplifier circuit is realized on two cascades, built on transistors with a common emitter. The total gain in this case is equal to the product of the coefficients of the individual cascades. Due to this, such a relatively large output power is achieved at the microphone amplifier output.
Since the circuit has not only a constant but also an alternating current to be amplified, it can affect the parameters of neighboring cascades along the path through the power supply. To eliminate this disadvantage, separate cascades are separated by filters. In addition, the variable component can be influenced not by the power source, which ultimately can lead to a violation of the operating mode of the circuit in direct current. Therefore, this video is devoted to the calculation of the parameters of such filters, which are an obligatory part in the microphone amplifier circuit.