LA8608V Datasheet, PDF (10/14 Pages) Sanyo Semicon Device – 1.8 V Low-Voltage Narrowband FM-IF System

LA8608V
Noise amplified by this amp passes through the noise detector, and is detected by R and C connected to pin 22. The Schmitt
circuit operates on the basis of this DC, and the Shmitt output appears on pin 13. Because the pass band gain is determined by
R2/R1, changing these resistances makes it possible to vary the Schmitt circuit level to some extent. By varying the level, it is
possible to continue operating Schmitt circuit up to a signal-to-noise ratio of approximately 30 dB on the No. 2 mixer input. To
continue operating Schmitt circuit at a higher S/N ratio, add a resistor between pin 17 and GND. This makes it possible to
increase the signal-to-noise ratio of the input level at which the Schmitt circuit continue operating by approximately 10 dB. (Refer
to Fig. 6.)
S/N for noise amp gain and Schmitt trigger
Misoperation when
Ri < 1 kΩ
With RB
Misoperation when
Ri < 12 kΩ
No R_B
Unit (resistance: Ω, capacitance: F)
Fig. 6
Sample application 2:
(1) When an operational amplifier is used in a signal system amplifier, etc., connect a capacitor of about 1000 pF between the
output (pins 17, 19, 21) and GND. This capacitor prevents local oscillation when the signal is clipped on the negative side.
Fig. 7
(2) When used in the signal system amplifier, etc. and the dynamic range of the output must be expanded, use the scheme
described below.
1) Use R_B1 to set the output DC voltage to
approximately 1/2V_CC .
Output DC voltage
V_ODC = V_B (1 + ^R2 ₎
R₃
V_B = 1 V
Fig. 8
2) Add 10 kΩ between the output pin and
GND.
No.4077 - 10/14