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July 1994 9
Philips Semiconductors Product specification
6 W hi-fi audio power amplifier TDA2613
Input mute circuit
The input mute circuit operates only during switching on and off of the supply voltage. The circuit compares the
1
⁄
2
supply
voltage (at pin 3) with an internally fixed reference voltage (V
ref
), derived directly from the supply voltage. When the
voltage at pin 3 is lower than V
ref
the non-inverting input (pin 9) is 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.5).
Fig.5 Input mute circuit; time delay.