SLFS022H – SEPTEMBER 1973 – REVISED JUNE 2010
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Pulse-Position Modulation
As shown in
any of these timers can be used as a pulse-position modulator. This application
modulates the threshold voltage and, thereby, the time delay, of a free-running oscillator.
shows a
triangular-wave modulation signal for such a circuit; however, any wave shape could be used.
V
CC
(5 V to 15 V)
4
RESET
2
TRIG
8
V
CC
OUT
R
L
3
R
A
Output
Voltage − 2 V/div
DISCH
Modulation
Input 5
(see Note A)
CONT
GND
THRES
7
R
B
6
C
Pin numbers shown are for the D, JG, P, PS, and PW packages.
NOTE A: The modulating signal can be direct or capacitively coupled
to CONT. For direct coupling, the effects of modulation
source voltage and impedance on the bias of the timer
should be considered.
Figure 20. Circuit for Pulse-Position Modulation
Figure 21. Pulse-Position-Modulation Waveforms
14
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ÎÎÎÎÎÎ
ÎÎÎÎÎÎ
Î
ÎÎÎÎÎÎÎÎÎ
ÎÎÎÎÎÎ
Î
ÎÎÎÎÎ
ÎÎÎÎÎ
ÎÎÎÎÎ
ÎÎÎÎÎÎÎ
ÎÎÎÎÎÎÎ
ÎÎ
ÎÎÎÎÎÎÎ
ÎÎÎÎÎÎ
ÎÎÎÎ
ÎÎÎÎÎ
ÎÎÎÎÎ
ÎÎÎÎÎ
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R
A
= 3 kΩ
R
B
= 500
Ω
R
L
= 1 kΩ
See Figure 20
Modulation Input Voltage
Output Voltage
Capacitor Voltage
Time − 0.1 ms/div
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