This is a 3 input mic mixer circuit using IC LM 741. Four 741s are used here. IC1, IC2, IC3 are used as preamplifiers. They produce a gain of around 40 decibel to the individual input signals. IC4 is wired as a summing amplifier to add the signals from three preamplifiers.IC4 also gives a gain of around 5 decibel to the final output signal. Total gain of the system is around 45 decibel.
Note:
• Use+15/-15 V DC dual power for powering this circuit.
• All inputs and output must be connected with respect to the ground.
• Capacitors C1, C2 and C3 must be rated 10V and other capacitors must be 30V.
General Description
Lay out IC LM 741
The LM741 series are general purpose operational amplifiers which feature improved performance over industry standards like the LM709. They are direct, plug-in replacements for the 709C, LM201, MC1439 and 748 in most applications. The amplifiers offer many features which make their application nearly foolproof: overload protection on the input and output, no latch-up when the common mode range is exceeded, as well as freedom from oscillations. The LM741C is identical to the LM741/LM741A except that the LM741C has their performance guaranteed over a 0°C to +70°C temperature range, instead of −55°C to +125°C.