Low-Cost Logarithmic Converter Using Opamp and Transistor

This low-cost logarithmic converter is built using op-amp and transistor. This circuit uses a Motorola MC1539G op-amp which is connected to PNP transistor. To compensate the error, this circuit need an external compensation which can accommodates wide range of input voltage and has about 200nA bias current. To adjust bias current initially, replace the transistor with 500K potentiometer and get […]

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20Hz High-Pass Rumble Filter, Subsonic Blocker

This is a schematic diagram of 20-Hz high-pass rumble filter circuit.  Rumble noise could come from many sources, such as wind blow around an outdoor microphone, mechanical disturbance on phonograph, or many other possibilities. We can remove this noise by filtering the signal before the amplifier. The This circuit is designed for 20-Hz cutoff frequency and phonograph amplifier with gain […]

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Fast Sample-And-Hold

Sample and hold circuit is used to pick a signal and hold the level at its output, making it useful for analog digital conversion or other application where the processing need a constant level signal for the input. The circuit that is shown in the schematic diagram below is one example of fast sample and hold circuit. This sample and […]

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