Elenco Electronics EP-130, Manual

Page: 94 / 160

In this project, we will make a microphone amplifier,
using the operational amplifier as a non-inverting
amplifier with two power sources. The earphone
works as a microphone.
Start by sliding the switch to position B and
completing the wiring for the circuit. When you finish
connecting the wires, set the switch to position A to
turn on the power, rotate the control fully clockwise,
and lightly tap your microphone – the earphone. The
tapping sound comes through the speaker.
When you use the earphone as a microphone, as in
this project, it’s better to remove the end that you put
in your ear. You can unscrew it by turning it counter-
clockwise. Turning the control adjusts the volume.
As you can see in the schematic, the dual
operational amplifier uses two power sources: 4.5V
for the circuit and 9V for the IC. Note that the dual
operational amplifier has two input terminals, the
positive (+) and negative (–) terminals 69 and 68.
The non-inverting input is applied to the positive (+)
terminal. The gain in strength of the signal through
this amplifier is about 100 – determined with the
formula R1/R2. Thus 100k/1k = a gain of 1.
Notes:
EXPERIMENT #75: NON-INVERTING TWO-POWER SUPPLY AMPLIFIER
Wiring Sequence:
o
1-29
o
2-30
o
3-67-90
o
27-69
o
63-131
o
68-89-75
o
70-134
o
121-135
o
122-132
o
124-119-26-76-5-14-EARPHONE
o
28-13-EARPHONE
-94-
Schematic