No. 5765-9/14

LA7567N, 7567NM

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Pin No.

Pin

Description

Equivalent circuit

6

7

8

EQ amp

• Equalizer circuit. This circuit is used to correct the video

signal frequency characteristics.

Pin 17 is the EQ amplifier input. This amplifier amplifies a

1.5-V p-p video signal to 2-V p-p.

• Notes on equalizer amplifier design

The equalizer amplifier is designed as a voltage follower

amplifier with a gain of about 2.3 dB. When used for

frequency characteristics correction, a capacitor, inductor,

and resistor must be connected in series between pin 7

and ground.

• Approach used in the equalizer amplifier

If vi is the input signal and vo is the output signal, then:

Where G is the voltage-follower amplifier gain.

Assume:

vin: Imaginary short

G: About 2.3 dB

vin

≈ 0.

Then:

• R1 is the IC internal resistance, and is 1 k

Ω. In the

application design, simply select Z to correspond to the

desired characteristics. However, since the EQ amplifier

gain will be maximum at the resonant point defined by Z,

care is required to assure that distortion does not occur.

9

APC FILTER

• PLL detector APC filter connection. The APC time constant

is switched internally in the IC. When locked, the VCO is

controlled by loop A and the loop gain is reduced. When

unlocked and during weak field reception, the VCO is

controlled by loop B and the loop gain is increased.

For this APC filter we recommend:

R = 150 to 390

Ω

C = 0.47 µF

R1

—— +1 (vi + vin) = Vo

× G

2

voG

R1

AV = —— = —— +1

vi

Z

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