Circuit Diagram Linear Optocoupler
This linear optocoupler is built with MOC5010 and can be used to isolate a circuit from main grid, audio interface, in medical electronics and many other applications. Because of its high isolation resistance (1011 Ω), MOC5010 is used in applications where a circuit is powered directly from main power. With a bandwidth from 5 Hz to 100 kHz you have no reason to complain about audio signal response.
MOC5010 transforms an input current variation into an output voltage variation. The linear optocoupler circuit presented here has an amplification factor of 0.75. The input must not overcome 2 Vef while bandwidth is 118 kHz at -3 dB.
Amplifier A has a transfer resistance of 200 mV/mA resulting in a total amplification of 0.6 … 0.8 (-4.5 … -2 dB). The output impedance is not higher than 200 Ω so you can connect an external amplifier at pin 4. If the input voltages are higher than 2 Vef then connect a potentiometer as voltage divider like showing below optocoupler circuit diagram.