PA3632

CMOS IC

UNISONIC TECHNOLOGIES CO., LTD

6 of 9

www.unisonic.com.tw

QW-R107-071.D

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APPLI CAT I ON I N FORM AT I ON

LINE DRIVER AMPLIFIERS

Single-supply line-driver amplifiers typically require dc-blocking capacitors. The top drawing in Figure 1 illustrates

the conventional line-driver amplifier connection to the load and output signal. DC blocking capacitors are often large

in value. The line load (typical resistive values of 600

Ω~10kΩ) combines with the dc blocking capacitors to form a

O

L

C

C

R

2

1

f





(1)

C

R

2

1

C





O

(2)

values require large package sizes. Large package sizes consume PCB area, stand high above the PCB, increase

cost of assembly, and can reduce the fidelity of the audio output signal.

The DirectPath amplifier architecture operates from a single supply but makes use of an internal charge pump to

provide a negative voltage rail. Combining the user-provided positive rail and the negative rail generated by the IC,

the device operates in what is effectively a split-supply mode. The output voltages are now centered at zero volts

with the capability to swing to the positive rail or negative rail. Combining this with the built-in click and pop reduction

circuit, the DirectPath amplifier requires no output dc blocking capacitors. The bottom block diagram and waveform

of Figure 1 illustrate the ground-referenced line-driver architecture. This is the architecture of the UTC PA3632.