AmplifierCircuits

General Description: Above schematic is for a three channel audio mixer. That will provide an overall gain of one between the output and each input channel. Each input channel includes a single 0.1uf capacitor and 100-Kilohms resistor to provide an output impedance of 100K. The number of input channels to this audio mixer can be increased by adding more capacitors and resistors with same value as capacitor(0.1uf) and resistor(100K). The mixer should be located between the output of tone control circuitry and the input to the power amplifier. One input should be taken from the output of the tone control circuit, and the other inputs should either be grounded or taken from desired source. Circuit diagram: Three Channel Audio Mixer circuit diagram

General Description: A new audio mixer circuit uses an LM3900 IC but is not a profesional audio dj mixer. The IC houses four integrated Norton amplifiers. The advantage of using the four op amps is that they only need a single power supply. Since this amplifier circuit is current controlled, the DC bias is dependent on the feedback coupling.The schematic diagram shows inverting AC-Norton amplifiers. The DC output must be set at 50 percent of the power supply. In this case, a maximum output can be achieved without distortion (also called symmetrical limitation through overdrive).In designing this mini audio mixer circuit diagram you can freely choose the value of the resistor R2 (100k in the mixer schematic). Set the AC voltage amplification factor through the ration of R2/R1. To set the amplifier gain correctly, choose the value of R4=2R2 (double the value of R2).Diagram 1.0 shows the 3-channel sound mixer circuit using three Norton-opamps. The input levels can be set by potentiomet...