LA8608V Datasheet, PDF (8/14 Pages) Sanyo Semicon Device – 1.8 V Low-Voltage Narrowband FM-IF System

IC Usage Notes
1. About the local oscillator
LA8608V
Fig. 1
Fig. 1 shows the equivalent circuit for the local oscillator.
In this circuit, when C₁ = 22 pF, the change in the negative resistance versus C₂ is shown in Fig. 2, the change in the operational
load capacitance is shown in Fig. 3, and the frequency deviation is shown in Fig. 4. In the application circuit,
C₂ = 120 pF, and in this case the negative resistance according to Fig. 2 is –58 Ω. In order to increase the negative resistance, it is
necessary to decrease the value of C₂. To increase the oscillation level, it is possible to add external resistor R₁ and raise the local
oscillator current. However, the oscillation level on pin 1 must be set to 110 dB or less. If set to a greater level, distortion will
occur in the oscillation waveform.
Fig. 2
Fig. 3
Fig. 4
(Note)
Fig 2 to 4: C1 = 22 pF
Figs. 3, 4: Reference to operating load
capacitance 16 pF
No.4077 - 8/14