TK83361MTL 查看數據表（PDF） - Toko America Inc
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TK83361MTL Datasheet PDF : 15 Pages
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TK83361M
APPLICATIONS INFORMATION (CONT.)
12-2. IF Section
The IF section includes a 6 stage differential amplifier. The
fixed internal input matching resistor is 1.8kΩ. The total gain
of the limiting amplifier section is approximately 77dB.
The decoupling capacitors of Pin 6~7 must be connected as
near as possible to the GND pin of the IC . And, make the
impedance of the connecting-to-GND line to be as small as
possible. If the impedance is not small enough, the sensitivi-
ties may worsen.
Figure 7: IF Limiter Amplifier Input Block
5
1.8k
6
7
50K
51.8K
Note at this point to add the bias voltage at Pin 8 from
external source.
The signal from the phase shifter is put into the multiplier cell
through the emitter follower of transistor Q1. Pin 8 is single-
connected with the base terminal. And, it is necessary for
Pin 8 to add the same voltage, as the base terminal of Q2 of
the opposite side of Q1 through the multiplier is connected
with the supply voltage.
If the base voltages differ between transistors Q1 and Q2, it
alters the DC zero point or worsens the distortion of the
demodulation output.
12-3-2. Phase Shifter
The IF signal from the limiter amplifier is provided with 90°
phase shift and drives the quadrature detector.
The parallel RCL resonance circuit is capable of using the
internal 10pF phase shift capacitor.
12-3-3. Audio Output
After quadrature detection, the audio signal is pulled out
through Pin 9.
The required signal is pulled out through the LPF.
12-3. FM Demodulator
A quadrature FM demodulator using a Gilbert cell is in-
cluded.
12-3-1. Internal Equivalent Circuit
The internal equivalent circuit is shown in Fig. 8.
Figure 8: Internal Equivalent Circuit of Demodulator
VCC
QUAD
COIL
RD
8
VCC
Q1
10pF
Active Load
VCC
Q2
12-3-4. For Stable Operation
To prevent worsening the distortion, observe the following
notes:
(1) Demodulated Output Voltage
Too large of a demodulated output voltage will worsen the
distortion due to the dynamic range of the demodulator.
(2) The Signal Level in Phase Shifter (Pin 8)
If the phase shifter signal level is too small, the noise level
grows worse. This will cause the distortion to grow worse.
(3) Band Width of Phase Shifter (Pin 8)
If the bandwidth of the phase shifter is narrower than IF
bandwidth, including the demodulated element, the distor-
tion will grow worse.
12-4. Filter Amplifier Section
An inverting op amp has an output at Pin 11 and the inverting
input at Pin 10. The op amp, which has a wide stable
operating temperature range, may be used as an active
noise filter.
Multiplier
Cell
12-4-1. Active BPF Application
An active BPF application is shown in Fig. 9, and its
Response is shown in Fig. 10.
Page 12
December 2000 TOKO, Inc.
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