LM555
Applications Information
(Continued)
00785113
V
CC
= 5V
TIME = 0.2 ms/DIV.
R
A
= 9.1kΩ
C = 0.01µF
Top Trace: Modulation 1V/Div.
Bottom Trace: Output Voltage 2V/Div.
00785115
V
CC
= 5V
TIME = 0.1 ms/DIV.
R
A
= 3.9kΩ
R
B
= 3kΩ
C = 0.01µF
Top Trace: Modulation Input 1V/Div.
Bottom Trace: Output 2V/Div.
FIGURE 9. Pulse Width Modulator
FIGURE 11. Pulse Position Modulator
PULSE POSITION MODULATOR
This application uses the timer connected for astable opera-
tion, as in
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.
shows the waveforms
generated for a triangle wave modulation signal.
LINEAR RAMP
When the pullup resistor, R
A
, in the monostable circuit is
replaced by a constant current source, a linear ramp is
generated.
shows a circuit configuration that will
perform this function.
00785116
00785114
FIGURE 12.
FIGURE 10. Pulse Position Modulator
shows waveforms generated by the linear ramp.
The time interval is given by:
V
BE
.
0.6V
9
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