TK14588 TOKO, TK14588 Datasheet - Page 13

• Manufacturer Part Number: TK14588
• Description: FM IF IC
• Manufacturer: TOKO

CIRCUIT DESCRIPTION
January 2000 TOKO, Inc.
IF Limiter Amplifier, RSSI:
The IF limiter amplifier is composed of five differential gain stages. The total gain of the IF limiter amplifier is 80 dB. The
output signal of the IF limiter amplifier is provided at Pin 14 through the emitter-follower output stage. The IF limiter amplifier
output level is 0.5 V
The input resistance of the IF limiter amplifier is 1.8 k (see Figure 1A). If the impedance of the filter is lower than 1.8
k , connect an external resistor between Pin 1 and Pin 2 in parallel to provide the equivalent load impedance of the filter.
Figure 1A shows the case that the impedance of the filter is 330 .
The operating current of the emitter-follower of the IF limiter amplifier output is 200 A. If the capacitive load is heavy, the
negative half cycle of the output waveform may be distorted. This distortion can be reduced by connecting an external
resistor between Pin 14 to GND to increase the operating current. The increased operating current by an external resistor
is calculated as follows (see Figure 1B):
The increased operating current I
P-P
330
.
FIGURE 1A
GND
e
1.8 K
(mA) = (V
CC
- 1.0) / R
e
(k )
+
-
AMP
V CC
COMP
V CC
100 k
FIGURE 1B
I e
IF OUTPUT
R e
TK14588
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