LA4165M Просмотр технического описания (PDF) - SANYO -> Panasonic

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LA4165M

Recording/Playback IC for Micro-Cassette Tape Recorder

SANYO -> Panasonic 

LA4165M

Functional Description

[Preamp]

• The frequency response characteristic of the low noise preamplifier is selected by the record/playback select pin

CONT (pin 20). If CONT is taken to ground to select record mode, the frequency response is flat. If CONT is left

open, playback mode is selected and the preamp has the NAM response curve.

[Power Amp]

• The power amplifier is suited to driving 4 Ω speakers and earphones.

[ALC]

• The ALC (Automatic Level Control) circuit is active in recording mode. It detects the power amp output level, and

controls the preamplifier input gain so that the power amp output level is constant.

[VOX CONT VOX]

• This circuit monitors the power amp output level, and turns the motor drive on or off. When the VOX CONT

circuit is operating, the LED drive output on pin 16 is active. The LED is extinguished if the supply voltage drops

to 1.8V.

[GVN]

• Motor control circuit. The external constants are determined according to the motor characteristics to keep the

motor speed constant.

Circuit Components

The function of each component, together with recommended values in parentheses, are listed below.

• C1: (2200 to 4700 pF)

Determines the frequency response of the signal voltage to the record/replay head during recording. Its value

should be selected according to the characteristics of the head.

• C2 : (4700 pF)

Determines the playback equalization frequency response.

• C3 : (2200 pF)

Suppresses high-frequency oscillation.

• C4 : (2200 to 4700 pF)

Controls high-frequency characteristics. C4 will interact with R3 to reduce the power amp input level if it is

too large.

• C5 : (2200 to 4700 pF)

Microphone input high-frequency filter. This should be selected according to the high-frequency cut-off and

the value of C21.

• C6 : (470 µF)

Couples the power amp output to the speaker or headphones. A value of 220 µF is adequate when using an 8 Ω

speaker or headphones.

• C7 : (1 µF)

Suppresses oscillation. For low-temperature operation (down to -10°C), a 0.47 µF tantalum electrolytic

capacitor should be used.

• C8 : (22 µF)

ALC control smoothing filter. C8 should not be too large, since this will also increase attack time.

• C9 : (0.1 to 2.2 µF)

Voice sensor (VOX) control smoothing filter. C8 should not be too large, since this will also increase turn-on

delay (the time for the motor drive circuit to turn on after the microphone input voltage reaches the set level).

Continued on next page.

No. 2824-7/17

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