Inverting Two-Power Supply Amplifier
Électronique / Electronic
Here's another two-power source microphone amplifier, but this one is an inverting amplifier. We use the earphone as a microphone again.
Slide the switch to position OFF and assemble the circuit.
When you finish the wiring, slide the switch to position ON to turn the power on, rotate the control clockwise, and speak into the microphone-the earphone. You will find that the project works just like our last project see Noninverting Two-Power Supply Amplifier in Operational amplifier section.
IC 1 is used as a buffer of gain 1, and IC 2 as an inverting amplifier. Input reaches this inverting amplifier through its negative (—) terminal, not the positive (+) one as in our last project. Its gain is about 100, as determined by: R1/R2 = 100K/1K.
The gain becomes larger if you increase R1 or decrease R2. See what happens to the gain when you change the value of R2 to 470 ohms.