LA1193M Просмотр технического описания (PDF) - SANYO -> Panasonic

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производитель

LA1193M

For Car Radios High-Performance FM Front End

SANYO -> Panasonic 

5. IF Amplifier

LA1193M, 1193V

This IF amplifier is a single stage differential amplifier.

Specifications

Input impedance : 330Ω

Output impedance : 330Ω

Gain :

25dB

Gain adjustment can be provided using either of the methods shown.

IF Gain adj

Temperature Characteristics

The LA1193M/V uses Vref temperature characteristics correction to hold the gain temperature characteristics to the

low level of about 1dB over the range −30 to +80°C.

6. AGC Circuit

The LA1193M/V uses pin diode antenna damping (pin 9) and MOSFET second gate voltage control (pin 16) for AGC.

The AGC operating sequence is as follows :

Antenna damping (pin diode) → MOSFET second gate voltage control

(attenuation) 20dB

(attenuation) dB

The above AGC sequence is used for the following reasons.

• Intermodulation distortion can occur if a signal of 110dBµ or larger is input to the antenna circuit varactor diode.

In such situations, if the AGC sequence was MOSFET second gate voltage control followed by pin diode antenna

damping, as long as the receiver was not in a strong field where the 60dB or higher AGC attenuation operates, input

limitation due to the antenna circuit varactor diode would operate. Therefore, we feel that the AGC operating

sequence employed is appropriate.

• Consider the problem of AGC loop stability. If the two AGC loops (the antenna damping AGC loop and the MOSFET

second gate control AGC loop) operate, the AGC system would become unstable and have an excessively large

influence on the transient response. Therefore the following structure cannot be used.

MOSFET second gate control → antenna damping → MOSFET second gate control

The AGC operating conditions are the same as those for the LA1175M.

• Narrow AGC circuit

Since the LA1193M/V’s N-AGC (which detects the mixer output) is set to have a high sensitivity, care is required to

avoid incorrect operation. In particular, there must be adequate separation from the local oscillator block on the

printed circuit board pattern. Also, a resistor of at least 500Ω must be inserted at the pin 13 input. A low-pass filter is

formed by the insertion of this resistor. This low-pass filter prevents incorrect AGC operation due to the local

oscillator.

• The AGC sensitivity setting can be changed by adjusting the

value of the capacitor connected at pin 13. Although the AGC

sensitivity can be lowered by increasing the value of the series

resistor, caution is required since the AGC has its own frequency

characteristics.

No.4715-12/22

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