NJU72040

– 9 –

APPLICATION NOTE

The NJU72040 is an audio headphone amplifier that eliminates the need for external dc-blocking output

capacitors. The NJU72040 has built-in pop suppression circuitry to eliminate disturbing pop noise during

power-on, power-off and mute-control.

1. Operating Principle

The NJU72040 has the built-in differential input operational amplifiers, voltage inverter, pop noise

suppression circuitry, gain selectable circuitry and thermal-overload protection circuitry (Fig.1).

For single-ended input signals, connect inverted terminal (INL-, INR-) or non-inverted terminal (INL+, INR+)

to ground through the capacitor. The voltage gain is selectable. In the differential circuitry, the setting gain is

The voltage inverter for NJU72040 eliminates the need for external dc-blocking output capacitors. The pop

suppression circuitry for NJU72040 eliminates the pop noise during power-on, power-off and mute-control.

Fig.1 The NJU72040 functional block diagram

1.1 External parts

form a high-pass filter with the corner frequency determined in [fc=1/(2

adjust 1uF or more.

INL-

INL+

OUTL

V+

CP

CN

GND

REF

MUTE

GAIN

INR-

INR+

OUTR

32Ω

Headphone

32Ω

Headphone

V+

inverted phase

inverted phase

C1

C2

C4

C6

C7

R2

C8

C10

V+

V+

V-

V-

Negative

Voltage

Regulator

Bias

Gain Select

Pop Noise

Suppression

Pop Noise

Suppression

3MΩ

100kΩ

Regulator

V+