LMC555
SNAS558J –FEBRUARY 2000–REVISED MARCH 2013
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PULSE POSITION MODULATOR
This application uses the timer connected for astable operation, as in Figure 14, with a modulating signal again
applied to the control voltage terminal. The pulse position varies with the modulating signal, since the threshold
voltage and hence the time delay is varied. Figure 15 shows the waveforms generated for a triangle wave
modulation signal.
Figure 14. Pulse Position Modulator
V
CC
= 5V Top Trace: Modulation Input 1 V/Div.
TIME = 0.1 ms/Div. Bottom Trace: Output Voltage 2 V/Div.
R
A
= 3.9 kΩ
R
B
= 3 kΩ
C = 0.01 µF
Figure 15. Pulse Position Modulator Waveforms
50% DUTY CYCLE OSCILLATOR
The frequency of oscillation is
f = 1/(1.4 R
C
C)
Figure 16. 50% Duty Cycle Oscillator
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