Monday, November 25, 2013

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USB Powered Audio Power Amplifier

circuit of multimedia speakers for PCs has single-chip-based design,
low-voltage power supply, compatibility with USB power, easy
heat-sinking, low cost, high flexibility and wide temperature tolerance.
At the heart of the circuit is IC TDA2822M. This IC is, in fact,
mono-lithic type in 8-lead mini DIP package. It is intended for use as a
dual audio power amplifier in battery-powered sound players.

of TDA2822M are low quiescent current, low crossover distortion,
supply voltage down to 1.8 volts and minimum output power of around 450
mW/channel with 4-ohm loudspeaker at 5V DC supply input. An ideal
power amplifier can be simply defined as a circuit that can deliver
audio power into external loads without generating significant signal
distortion and without consuming excessive quiescent current.

circuit is powered by 5V DC supply available from the USB port of the
PC. When power switch S1 is flipped to ‘on’ position, 5V power supply
is extended to the circuit and power-indicator red LED1 lights up
instantly. Resistor R1 is a current surge limiter and capacitors C1 and
C4 act as buffers. Working of the circuit is simple. Audio signals from
the PC audio socket/headphone socket are fed to the amplifier circuit
through components R2 and C2 (left channel), and R3 and C3 (right

Circuit diagram:
usb operated multimedia speaker circuit schematic

VR1 works as the volume controller for left (L) channel and potmeter
VR2 works for right (R) channel. Pin 7 of TDA2822M receives the
left-channel sound signals and pin 6 receives the right-channel signals
through VR1 and VR2, respectively. Ampl i f ied signals for driving the
left and right loudspeakers are available at pins 1 and 3 of IC1,
respectively. Components R5 and C8, and R6 and C10 form the traditional
zobel network.

Assemble the circuit on a medium-size,
general-purpose PCB and enclose in a suitable cabinet. It is advisable
to use a socket for IC TDA2822M. The external connections should be made
using suitably screened wires for better result.

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