BA4424 Просмотр технического описания (PDF) - ROHM Semiconductor

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Компоненты Описание

производитель

BA4424

FM / TV front end

ROHM Semiconductor 

Audio ICs

FMeasurement circuit

BA4424N

FPin connections

1 FM ANT input pin

: Connect to BPF ZIN =

75Ω

2 RF amplifier bypass pin : Connect to bypass ca-

pacitor

3 RF amplifier output load pin : Connect to RF tuning

circuit

4 MIX output pin

: IFT or resistor load

5 GND pin

: IC ground pin

FCircuit operation

(1) RF amplifier circuit

The RF amplifier consists of a common base transistor.

A band pass filter (BPF) is used in the ANT circuit, and

as the RF amplifier is base-grounded, a BPF with an out-

put impedance of 75Ω should be used. If a BPF without

DC cutoff is used, a coupling capacitor will be necessary.

An LC tuning circuit is connected to form the output load

of the RF amplifier. A coil with tap or coil with secondary

winding can be used to reduce spurious ratios such as

image ratios. A coupling capacitor for the mixer circuit is

included on-chip. The bypass capacitor for the RF ampli-

fier should have good high frequency characteristics,

and it should be connected to the input BPF ground con-

nection as close as possible to Pin 5 (GND), such that the

connection pattern absolutely does not allow supply cur-

rent to flow from Pin 5.

6 IF amplifier output pin

7 AFC diode pin

8 OSC pin

9 VCC pin

: ZOUT = 330Ω

: Cathode pin (anode pin

is connected internally

to ground)

: Connect to resonating

circuit

: IC voltage supply pin

50

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