For the IC Audio Amplifier, we use the integrated circuit
(IC) LM-386. In Figure 11, you can see equivalent
schematic and connection diagrams.
To make the LM-386 a more versatile amplifier, two
pins (1 and 8) are provided for gain control. With pins
1 and 8 open, the 1.35k
W
resistor sets the gain at 20
(see Figure 12a). The gain will go up to 200 (see Figure
12b) if a capacitor is placed between pins 1 and 8. The
gain can be set to any value from 20 to 200 if a resistor
is placed in series with the capacitor.
The amplifier in our kit with a gain of 50 is shown in
Figure 13. Capacitor C11 couples the audio signal from
the volume control to the input of the audio amplifier.
Capacitor C13 blocks the DC to the speaker, while
allowing the AC to pass.
-16-
SECTION 1B
INTEGRATED CIRCUIT (IC) AUDIO AMPLIFIER
Figure 12a
Figure 12b
Figure 13
Dual In-Line and Small Outline Packages
Top View
Figure 11
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