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CXA1998BQ

Recording/Playback Equalizer Amplifier

Sony Semiconductor 

CXA1998BQ

(2) AMS level setting

The AMS level is set by adjusting HPF gain and cut-off frequency with the external resistor and capacitor at

Pin 9.

G and fc in Fig. 2 are obtained from the following formula.

G = 20log (1 + 100k/R1) [dB]

(1)

fc = 1 / (2 · π · C1 · R1) [Hz]

Full-wave rectifier is applied for the signal at DET.

Signal detection time is set by the time constant of Pin 11 external resistor and capacitor.

DET signal detection level:

= –7.5dBm (typ.)

= playback equalizer reference output level + AMS level + HPF gain

(2)

Playback equalizer reference output level of –21dBm is 0dB.

Ex.)

To set AMS level at –25dB, determine and set the constant for Pin 9 external resistor.

(Calculate assuming PBOUT1 = PBOUT2)

First, get the required HPF gain from formula (2).

–7.5dBm = –21dBm + (–25dB) + HPFgain,

so HPF gain = 38.5dB.

Next, get Pin 9 external resistance from formula (1).

38.5dB = 20log (1 + 100k / R1),

so R1 ≈ 1.2kΩ,

and external resistance is 1.2kΩ.

– 23 –

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