BA3528 Ver la hoja de datos (PDF) - ROHM Semiconductor

Número de pieza

componentes Descripción

Fabricante

BA3528

Pre / power amplifier and motor governor for 3V headphone stereos

ROHM Semiconductor 

Audio ICs

FCircuit operation

(1) Preamplifier

In the preamplifier input stage the pin 22 bias is the input

and the negative feedback virtual earth, and the bias for

the input stage transistor is taken from pin 22 via the tape

head to allow direct coupling. Connect a 1000pF capaci-

tor in parallel with the tape head to prevent high-frequen-

cy interference (see Fig. 2).

BA3528AFP / BA3529AFP

(4) Power amplifier

The power amplifier employs an NF circuit with fixed

gain. GVC = 36dB (BA3528AFP) and GVC = 27dB

(BA3529AFP).

(2) Mute amplifier

Preamplifier output muting can be switched on and off.

The mute is off when the mute switch input (pin 1) is low

or open, and on when the mute switch input is high (tied

to VCC via a resistor), see Fig. 3.

For the input stage, the pin 22 bias point is the input and

the negative feedback virtual earth point, and the first

stage transistor bias is taken from pin 22. The built-in VREF

amplifier uses the same bias point as its input, and its out-

put voltage is about the same as DC output voltage from

the power amplifier. This becomes the virtual earth for the

headphones (see Fig. 5).

(3) Equalizer

The preamplifier is based on an NAB120µs NF-type

equalizer. It is possible to add a switching function for the

equalizer using the mute amplifier. Switching of the

equalizer constant is controlled by the voltage on pin 1

(low or high). Note, however, when this is done, preampli-

fier muting no longer operates (see Fig. 4).

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