Philips TDA1521A

July 1994 8

Philips Semiconductors Product speciﬁcation

2 x 6 W hi-ﬁ audio power ampliﬁer TDA1521A

APPLICATION INFORMATION

Input mute circuit

The input mute circuit operates only during switching on and off of the supply voltage. The circuit compares the1⁄2supply

voltage (at pin 3) with an internally fixed reference voltage (Vref), derived directly from the supply voltage. When the

voltage at pin 3 is lower than Vrefthe non-inverting inputs (pins 1 and 9) are disconnected from the amplifier. The voltage

at pin 3 is determined by an internal voltage divider and the external 100 µF capacitor.

During switching on, a time delay is created between the reference voltage and the voltage at pin 3, during which the

input terminal is disconnected, (as illustrated in Fig.3).

Fig.3 Input mute circuit; time delay.