la1175 Sanyo Semiconductor Corporation, la1175 Datasheet - Page 13

• Manufacturer Part Number: la1175
• Description: Fm Mixer, If, Agc Driver, Buffer For Car Radios, Stereo Systems
• Manufacturer: Sanyo Semiconductor Corporation

Description of AGC circuit in the LA1175, 1175M
The LA1175, 1175M are designed so that AGC is operated in the order shown below.
The following are the reasons why AGC is operated in this order.
(1) When a signal of 110dBµ or greater is applied to the varactor in the ANT circuit, intermodulation may occur. In
(2) If the two AGC loops (AGC loop (ANT damping) and AGC loop (MOS FET 2nd gate control)) are operated
this case, if AGC is operated in the order of MOS FET 2nd gate control AGC
input to the varactor in the ANT circuit is not restricted unless a strong signal with AGC attenuation 60dB or
greater is given. Therefore, AGC should be operated in the order shown above.
simultaneously, the transient response of AGC loses stability. Therefore, the order shown below is
impracticable.
ANT damping (PIN diode)
MOS FET 2nd gate control
(Attenuation)20dB
Temperature Characteristic (7)
Temperature Characteristic (7)
Ambient temperature, Ta – °C
Ambient temperature, Ta – °C
MOS FET 2nd gate voltage control
ANT damping
(Attenuation)60dB
LA1175, 1175M
MOS FET 2nd gate control.
Temperature Characteristic (7)
Ambient temperature, Ta – °C
ANT damping (PIN diode), the
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