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  • Multi-channel audio mixer circuit using LM3900

  • Created: Jan 07, 2016

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The LM3900 is a 14-pin device designed to operate for a single supply over a wide range of voltages that provide a large output swing in the output voltage. It contains four independent, high gain frequency Norton op-amp use specifically for this IC. Unlike traditional op-amp that respond to differential voltages, LM3900 utilizes the differential current.

The operation of the circuit is simple. The input side is composed of two audio mic inputs and two direct lines. Audio input is being amplified separately and it is connected in the inverting side (-) of each op-amp. C1 to C5 are decoupling capacitors that greatly help in reducing the noise in the circuit. The output side of each channel is connected to a single output line which is connected to the pre-amplifier and produces the desire mixed audio output with less noise.

LM3900 has also a wide bandwidth and internal frequency compensation. It has also a low input bias current. Some of the other applications of LM3900 are AC/DC amplifier, voltage regulator, RC active filter,waveform generators, PLL and VCO, digital and switching circuits.



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