UPC2533GS Ver la hoja de datos (PDF) - NEC => Renesas Technology

Número de pieza

componentes Descripción

Fabricante

UPC2533GS

AM TUNER FOR ELECTRONIC TUNING CAR RADIOS

NEC => Renesas Technology 

µPC2533

2. Operation of Each Block

2.1 FR Amplifier Circuit Block

VCC

R1

C8

L3 R2

Q1

+

L1

Q2

C9

L2

C1

C2

Fig. 2-1 RF Ampliier Circuit

LPF

L4 L5

C6

33

C3 C4 C5

30

C7

35

36

34

+

MIX1

RF AGC

From MIX2

LO/DXNote

4

Note LO : 3 V or higher

DX : 1 V or lower

In the AM band, the capacitance of a car radio antenna depends on its length, diameter, cable length, etc. Therefore,

J-FET is used in the µPC2533 to raise RF input impedance.

Since the µPC2533 raises the first IF (intermediate frequency) to 10.71 MHz, there is no need for a tuning circuit

between the RF amplifier circuit and MIX1. Instead, it employs an LPF (about 6 MHz) consisting of L4, L5 and C3

to C5 between the RF amplifier circuit and MIX1 in order to cut image frequency (21.4 MHz or higher). Because this

allows a wide-band RF amplifier circuit to be configured without using a tuning circuit, frequency sensitivity deviation

can be minimized to a high degree.

The AGC circuit consists of RF AGC1 by the PIN diode connected to the FET gate and RF AGC2 by the cascade

transistor Q1. Use a low-noise transistor even with low current for the cascade transistor Q1 (if a high-noise one is

used, the S/N ratio deteriorates).

Remark Set bias voltage for cascade transistor Q1 to VC > VB.

11

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