822

Audio ICs

BA3126F / BA3126N

FCircuit operation

(1)

Playback mode

When the control pin voltage goes below 0.5V, the REC

SW goes off and the P / B SW goes on to put the IC into

playback mode. In this mode, the playback signal from

the head is sent to the P / B amplifier via the REC SW.

(2)

REC mode

When the control pin voltage goes above 3.9V, the P / B

SW goes off and the REC SW goes on to put the IC into

record mode. In this mode, the recording signal from

REC amplifier is transmitted to the head via the P / B

SW.

FOperation notes

(1)

When the voltage on the control pin drops below

0.5V, (pin 5 for the BA3126F, and pin 4 for the BA3126N)

the IC switches to P / B mode . When the voltage is 0V,

the maximum source current generated is 120

When the voltage on the control pin goes above 3.9V the

IC switches to REC mode. When the voltage is 5V, the

maximum sink current generated is 180

mately 2.0V). All switches are on at this time.

(2)

P / B switch (BA3126F : pins 3 and 12, BA3126N

: pins 3 and 7)

This switch is on during playback. Due to the characteris-

tics of the transistor switch, the following DC voltage is

generated :

This switch is off during recording. A built-in, high-with-

standing voltage switch means that it can handle the

large-amplitude bias signal generated by the bias gener-

ator.

Due to variations between individual ICs, we recommend

(3)

REC switch (BA3126F : pins 1 and 14, BA3126N :

pins 1 and 9)

This switch is on during recording. Due to the character-

istics of the transistor switch, the following DC voltage is

generated :

The switch is off during playback, and the playback signal

from the head is transmitted to the playback amplifier.

(4)

Recommended operating power supply voltage

range

Operation of the basic functions of the application exam-

ple circuit are guaranteed if operated within the stipulated

power supply voltage and ambient temperature ranges.

We cannot guarantee the ratings for the electrical char-

acteristics, but they will not change radically if the circuit

is operated within the stipulated power supply voltage

and ambient temperature ranges.

(5)

Transient characteristics during power supply

switching

When the power is switched on and of in P / B mode

(control pin low), a transient current may flow from the

P / B SW to the REC SW.

If the head is in contact with the tape, and this current

flows into the head, the frequency component will be re-

corded as a pop sound on the tape. Pay due consider-

ation to the power supply on / off timing and the head

position relationship.

(6)

Playback-to-recording switching timing

If a large-amplitude signal from the bias oscillator is ap-

plied when the P / B SW is on, the P / B switch may latch

if there is excessive current from the bias oscillator. If this

happens, the P / B SW will not switch off when the con-

trol pin is driven high, and the IC will not enter REC mode.

Design the timing so that when the IC is switched from

playback to recording mode, the P / B SW goes off be-

fore the large-amplitude signal from the bias oscillator is

applied to the P / B SW.