NJU72011 datasheet(9/15 Pages) NJRC

9 / 15 page

NJU72011

– 9 –

APPLICATION NOTE

The NJU72011 is an audio line amplifier that eliminates the need for external dc-blocking output capacitors.

The NJU72011 has built-in pop suppression circuitry to eliminate disturbing pop noise during power-on,

power-off and mute-control.

1. Operating Principle

The NJU72011 has the built-in non-inverted input operational amplifiers, voltage inverter, and pop noise

suppression circuitry (Fig.1).

The voltage inverter for NJU72011 eliminates the need for external dc-blocking output capacitors. The pop

suppression circuitry for NJU72011 eliminates the pop noise during power-on, power-off and mute-control.

Fig.1 The NJU72011 functional block diagram

1.1 External parts

1.1.1 Input coupling capacitors Ci (C2, C8)

The input coupling capacitor (Ci) and the total of the external resistance (R1, R3) and the input

resistance (Rin=218kΩ typ.) for the non-inverted terminal form a high-pass filter with the corner

frequency determined in [fc=1/(2

π x (R1+218kΩ) x Ci)). It is necessary to adjust 1uF or more.

Mute-Tr

1uF

10uF

V+

1uF 1kΩ

820pF

Charge

Pump

Bias

INL

OUTL

V+

INR

OUTR

GND

MUTE

1uF

1kΩ

820pF

10uF

4.7uF

22kΩ

V-

Pop Noise

Suppression

C11

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