A Simple Digital Audio Amplifier

Using a CMOS IC in an analog circuit

Analog circuits have had their day; everything is digital now. Here we present a simple digital amplifier built with standard CMOS logic gates, which digitizes the analog audio signal and then converts it back to analog for output to the loudspeaker. Along with being interesting, this project can be used as the basis for countless experiments.The core element of the circuit is a square-wave oscillator consisting of an inverting logic gate and an RC network.

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Materials

A Simple Digital Audio Amplifier

www.ti.com/lit/an/scha004/scha004.pdf

CAD data

Component list

Component List
Resistors
R1 = 33Ohm (optional, in parallel with loudspeaker)
R2 = 2.2kOhm
R3 = 100kOhm
P1 = 100kOhm trimpot, multiturn
P2 = 10kOhm potentiometer, linear
Capacitors
C1 = 100µF, 25V
C2 = 470µF, 63V
C3 = 330pF
C4,C5 = 1µF, tantalum
Inductors & Transformers
L1 = 47µH
Semiconductors
D1–D4 = 1N4001
T1 = BS170
T2 = BS250
IC1 = 4049UBE or 4069UBE