30k

) R1 ) R2

G = 20

log

R1

) R2

(dB)

1

2

π C

(R1

) R2)

(Hz)

5.4

C

I

(S)

1/2

)2.0

2.0

(S)

276

Audio ICs

BA3430S / BA3430F / BA3430FS

Equivalent circuit schematic

R2 is a resistor inside the IC which is 100

Ω during play-

back and 360

Ω during fast forward.

The gain of the amplifier is

This circuit detects the presence or not of the signal and

outputs a detection signal.

The circuit consists of two comparators. The first

comparator detects the level of the signal and the second

comparator detects the duration of the signal.

comparator turns on and draws a constant current I from

the time constant pin. This causes the voltage of the time

the next comparator turns on, changing the mute detec-

tion output pin to low.

comparator turns off and the voltage of the time constant

pin rises due to the external discharge resistor. When this

turns off, changing the mute detection output pin to high.

of the mute detection output pin to low is given as follows:

This equation holds when the input signal is sufficiently

large.

See Fig. 20 for the small signal time

The time

over of the mute detection output pin to high is as follows:

I: Output current of first comparator = approx. 1mA

C: External capacitor connected to time constant pin

R: External resistor connected to time constant pin (this

should be 22k

Ω or higher)

Equivalent circuit schematic