Elenco 130-in-1 Electronics Playground - Manual (Page 91)

-91-
In this experiment, you will make a microphone
amplifier, using the operational amplifier (op amp) as
a non-inverting amplifier with two power sources. The
earphone acts as a microphone.
Begin by sliding the switch to position B and finishing
the wiring for the circuit. When your wiring is ready,
set the switch to position A to turn on the power. Now
rotate the control fully clockwise, and lightly tap your
“microphone” – the earphone. The tapping sound is
heard through the speaker.
The earphone is a better microphone if you remove
the end that you put in your ear, by turning it counter-
clockwise to unscrew it. To adjust the volume, turn
the control.
As you can observe in the schematic, the operational
amplifier uses two power sources: 4.5V for the circuit
and 9V for the IC. The signal from the earphone is
connected to the operational amplifier’s non-inverting
input through the control. The input is amplified, and
the output is applied to the transformer. The gain
through the amplifier is about 100, determined by the
ratio R1/R2 (100k
Ω
k k / 1k
Ω
k = 100).
Notes:
EXPERIMENT #72: NON-INVERTING DUAL SUPPLY OP AMP
Wiring Sequence:
1-29
2-30
3-67-90
27-69
63-131
68-89-75
70-134
121-135
122-132
124-119-26-76-5-14-EARPHONE
28-13-EARPHONE
Schematic