13. Pulsed waveforms and Timing Circuit Design 13.1 Op. Amp

1
13. Pulsed waveforms and Timing Circuit Design

• 13.1 Op. Amp. Pulse Generators
• 13.2 555 timer IC Oscillator
• 13.3 555 Timer Variable Duty Cycle Circuits
• 13.4 555 Timer Monostable Circuits

2
13.1 Op. Amp. Pulse Generators
Study example 14.7-page786 for this pulse
generator with diode
3
Summary of Design Equations Op. Amp. Pulse
Generators
4
Example Given the Op. Amp. Pulse Generator
circuit below, (a) calculate and sketch the
output waveform (b) frequency output and (c)
duty cycle of the output waveform if C 0.1mF, R
20kW, R1 R2 R3 1kW.
5
Example Design the Op. Amp. Pulse Generator
circuit to generate a 500Hz waveform at a duty
cycle of 20. (a) Sketch the output waveform (b)
Design all charging and discharging resistors if
C 0.1mF and voltage divider resistors R1 R2
1kW to provide threshold voltage to the generator.
6
13.2 555 timer IC Oscillator
555 Timer
7
(No Transcript)
8
Astable Multivibrator (pulse generator)
9
Pulse frequency and duty cycle
10
Continuous and step Pulse frequency
Discharge R2 is varied to get continuous change
of discharge time td which will vary both
frequency and duty cycle
R1 is varied to change charge R1 R2 to get
continuous change of charge time tc which will
vary both frequency and duty cycle
Decade step of capacitor C1 10C2 , C210C3 is
switched to get step change of T which will
vary the frequency but duty cycle remains the same
11
13.3 555 Timer IC Variable Duty Cycles Circuits
By using a diode to bypass R2 while charging the
capacitor, the tc is found from R1 alone and td
is found from R2 alone.
Now tc CR1ln2 and td CR2ln2 Duty(CR1ln2)/(CR1l
n2 CR2ln2 ) R1/(R1R2)
If R2 R1 then duty cycle 50 If R2 gt R1 then
duty cycle gt 50 If R2 lt R1 then duty cycle lt 50
12
13.4 555 timer IC Monostable Circuit
Monostable Multivibrator (timer)
13
Summary of Design Equations 555 Oscillator and
Timer
Astable Multivibrator 1
Astable Multivibrator 2
Astable Multivibrator 3
Monostable Multivibrator
14
Example Design the 555 Timer IC Pulse Generator
circuit to generate a 500Hz waveform at a duty
cycle of 80. (a) Sketch the output waveform (b)
Design all charging and discharging resistors if
C 0.1mF (c) Sketch the circuit.
15
Example Design the 555 Timer IC Pulse Generator
circuit to generate a 500Hz waveform at a duty
cycle of (a) 50. (b) 20 (c) 80 Design all
charging and discharging resistors if C 0.1mF
(c) Sketch the circuit.
16
Example Design the 555 Timer IC Pulse Generator
circuit to generate a 20Hz to 250Hz waveform by
using a minimum discharge resistance of 1kW. (a)
Sketch the output waveform (b) Design all
charging and discharging resistors if C1 0.1mF
(c) Sketch the circuit (d) what is the maximum
frequency of this generator if a decade step uses
2 more capacitors C20.01mF, C30.001mF?
17
Example Design the 555 Timer IC circuit to
generate a 100ms pulse. (a) Design C if charging
resistors is 1MW (b) Sketch the circuit.