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PRODUCT SPECIFICATION
RC2211A
9
Design Examples
Tone detector with a detection band of 1 kHz
±
20 Hz:
Step 1: Choose R
0
= 20 k
W
(18 k
W
in series with 5 k
W
potentiometer) .
Step 2: Choose C
0
for F
0
= 1 kHz: C
0
= 0.05
m
F.
Step 3: Calculate R
1
: R
1
= (R
0
) (1000/20) = 1 M
W
.
Step 4: Calculate C
1
: for
z
= 1/2, C
1
= 0.25
m
F,
C
0
= 0.013
m
F.
Step 5: Calculate C
D
: C
D
= 16/38 = 0.42
m
F.
Step 6: Fine tune the center frequency with the 5 k
W
potentiometer. R
X
.
Linear FM Detection
The RC2211A can be used as a linear FM detector for a wide
range of analog communications and telemetry applications.
The recommended circuit connection for the application is
shown in Figure 5. The demodulated output is taken from the
loop phase detector output (pin 11), through a post detection
filter made up of R
F
and C
F
, and an external buffer amplifier.
This buffer amplifier is necessary because of the high
impedance output at pin 11. Normally, a non-inverting unity
gain op amp can be used as a buffer amplifier, as shown in
Figure 5.
The FM detector gain, i.e., the output voltage change per unit
of FM deviation, can be given as:
V
OUT
= R
1
V
R
/100 R
0
Volts/% deviation
where V
R
is the internal reference voltage. For the choice of
external components R
1
, R
0
, C
0
, C
1
and C
F
, see the section
on Design Instructions.
Figure 5. Linear FM Detector
Using RC2211A and an External Op Amp
65-2211-08
(12)
(11)
R1
R
F
100K
R0
C1
C
F
+V
S
Demodulated
Ouput
(14)
(13)
(2)
FM
Input
CK
C
O
0.1
μ
F
0.1
μ
F
+V
S
0.1
μ
F
RC2211A
(8)
(1)
(10)
(4)