Circuits of audio pre-Amp mic

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A microphone preamp is a preamplifier used to amplify a microphone's low output voltage to a stronger, more usable level. A microphone preamp must provide stable gain for small signals without being sensitive to induced noise from cabling and without distorting large amplitude signals. Most microphones must be used in conjunction with a microphone preamp to function properly.

Simple audio Pre-Amp mic

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This circuits use infront an RF oscilator to make an RF transmitter that is very sensitive to sound

Circuits of Infra Red Sensor

type='html'>Circuit of Movement detectors


Photodioda as removing the transmitter beam infra red with the pulsation frequency 5KHz, then the pulsation will be reflection by reflector in front of it. and received by the phototransistor as the receiver. The detected object is located between the transmitter-receiver with a reflector.

Circuit on the left is the transmitter modulation circuit that produces infrared 5KHz throbbing. On the right side is the receiver circuit, there is a resonance tuned amplifier. Band width it can control so the receiver circuit can catch the beat of the transmitter modulation 5Khz. Bandwidth control is also working to reduce the sensitivity of the effect of light in the surrounding areas.

Circuits of Audio Booster

type='html'>Audio booster with transistor


The 2N3392 transistor is a (cheap) low-power, low-noise and high-gain. If you wish to use a TUN, cross reference the parameters with one of the units from this list:

Potentiometer R5 of 100K is a linear type. The value of C1 may need to be between 0.05uF and 0.1uF (47nF/100nF). Experiment with the value for best performance.
Capacitor C3's working voltage should be at least 16V.