CXA1665AM-S 데이터 시트보기 (PDF) - Sony Semiconductor
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CXA1665AM-S Datasheet PDF : 10 Pages
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CXA1665AM/AM-S
Description of Operation (See Electrical Characteristics Test Circuit.)
(1) VHF oscillator circuit
The differential oscillator circuit with an output at Pin 16 and an input at Pin 1.
Connect an LC resonance circuit comprising a varicap diode to Pin 16 through a coupling capacitor. The
positive feedback from the resonance circuit is applied to Pin 1 through a feedback capacitor to execute
oscillation. Note that if a parasitic capacitance across Pins 1 and 16 is too large, it may cause undesired
oscillation.
(2) VHF mixer circuit
This is a double-balanced mixer having small leakage of local oscillation signal. The RF signal is input to Pins
7 and 8. In normal use, the signal is input to one pin while the other pin is connected to GND by decoupling
capacitor. The RF signal is converted to IF with the signal supplied from oscillator. The converted RF is sent to
the IF amplifier and output to Pins 3 and 4 simultaneously.
(3) UHF oscillator circuit
UHF oscillator is formed from two collector-grounded Colpitts oscillator, and oscillation is provided at the
differential input through an LC resonator circuit including a varicap diode.
The Pin 12 also functions as UHF/VHF switch pin.
(4) UHF mixer circuit
This is the double-balanced mixer like the VHF mixer. The RF signal is input to Pins 9 and 10. There is a
balanced differential input from pre-stage double tune circuit, or an unbalanced input to Pin 9 with the capacitor
connected at Pin 10 to GND. Balanced input achieves better NF rather than unbalanced input.
Otherwise, the conditions and usage are the same as those for the VHF mixer circuit.
(5) IF amplifier circuit
The mixer output signal is amplified by the IF amplifier and output to Pin 5. The output impedance is about
75Ω.
(6) UHF/VHF switch circuit
UHF/VHF mode is selected by the DC voltage at Pin 12. UHF operation is chosen by inputting 9V through a
20kΩ resistor, and VHF operation by inputting 0V. If the UHF switch voltage is 12V not 9V, adjust the
resistance to approximately 30kΩ so that the DC voltage becomes almost equal between Pins 12 and 15. Be
sure to connect a resistor for discharging (approx. 10kΩ) if OPEN not 0V is chosen for the VHF switch voltage.
Note on Usage
Care should be taken such as grounding in placing external parts because high frequencies are present.
Adjust accordingly to prevent heat problems with special care such as the GND pattern for heat dissipation at
the portion for IC mount where heat dissipations accumulate.
–6–
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