BA4424 データシートの表示（PDF） - ROHM Semiconductor

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BA4424

FM / TV front end

ROHM Semiconductor 

Audio ICs

FOperation notes

(1) Application circuit

The example application circuit is the one which we rec-

ommend, however, when using it, verify characteristics

carefully.

If external circuit values are changed, set them with suffi-

cient margin to allow for deviations of both the Rohm IC

and external components in the quiescent and transient

characteristics. Also, please note that we have not com-

pletely verified any possible patent issues which the ap-

plication circuit may involve.

(2) Operating power supply voltage range

As long as the operating power supply voltage range is

not exceeded, the circuit functions are guaranteed within

the ambient operating temperature. Although we cannot

guarantee that the electrical characteristic values rated

under the rating conditions will be obtained, there will be

no abrupt changes in the characteristics within this

range.

(3) RF amplifier

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 must be used. If a BPF without DC

cutoff is used, a coupling capacitor will be necessary.

Connect the bypass capacitor to the ground connection

of the input BPF. The pattern connecting these should be

such that supply current will absolutely not flow from Pin

5 (the ground line should be laid in the same fashion as

shown in the measurement circuit schematic).

BA4424N

(4) Mixer load

In addition to an IFT, a resistive load can also be used for

the mixer output load. However, take care in this case as

the gain and intermodulation characteristics will be af-

fected.

(5) Local oscillation circuit

To reduce spurious radiation, the oscillation level at Pin

8 (OSC) can be adjusted. This is done by adding a resis-

tor (several Ω to several tens of Ω) between Pin 8 and the

tank circuit. However, when setting the value, take care

regarding the oscillation margin as related to the tank cir-

cuit Q damp.

(6) IF buffer amplifier

If the buffer amplifier pin is connected to another circuit

to use the buffer amplifier pin’s voltage, take care that a

reverse voltage never appears at the pin.

(7) Power supply RC filter

Do not insert a resistor between the VCC pin (Pin 9) and

the MIX OUT pins (Pins 3 and 4), as a resistor inserted

in the power supply line will decrease sensitivity due to

the drop in the voltage. Regarding the resistor between

Pin 9 and the RFout pin (Pin 3), set the value so that the

voltage at Pin 3 is not lower than the voltage at Pin 2.

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