Électronique / Electronic
In Projects Noninverting Two-Power Supply Amplifier and Inverting Two-Power Supply Amplifier in OP AMP section, we used the operational amplifier with two power sources. In this project, we make a single-power source, noninverting microphone amplifier. Again, the earphone works as a microphone.
Slide the switch to position OFF and assemble the circuit. When you finish the wiring, slide the switch to position ON to turn on the power, rotate the control clockwise, and speak into the microphone.
The project works just like Projects Noninverting Two-Power Supply Amplifier and Inverting Two-Power Supply Amplifier, but you'll notice something different. The difference comes from the gain of this microphone amplifier. It is still determined by R1 and R2, but now it's much larger. Can you see why?
Yes, we use the 100 ohm resistor in place of the 1Κ ohm resistor from the last two projects. Try changing R2 to 1K, and the gain drops to the level of the last projects.
In this project, the two power sources are connected in series to operate the dual operational amplifier at 9V. But the operational amplifier can work at half this voltage, at 4.5V. See what happens when you disconnect the operational amplifier from + battery terminal of the first battery and connect it to + terminal of second.