15ecl48 VTU Raghudathesh Astable Monostable Multivibrator

LIC & AC Lab Manual

CBCS Scheme

15ECL48

Astable Multivibrator Aim: To Design a Asatble Multivibrator using a IC555 Timer to generate a square wave of desired frequency and duty cycle.

Components required: Sl No 1 2 3 4 5 6 7 8

Components IC555 Capacitors DRB DC Supply CRO Bread Board CRO Probes Connecting Wires

Specification 0.1 µF, 0.01 µF -

Quantity 1 1 each 1 1 1 1 2 1 set

Theory: Circuit Diagram:

Figure 1: Astable Multivibrator

Dept ECE, GMIT, Davangere

Page 1

LIC & AC Lab Manual

CBCS Scheme

15ECL48

Circuit Design: Assume f = 2 kHz and duty cycle of 70 %. Consider C = 0.1 µF.

Duty Cycle 

Waveforms:

Figure2: Capacitor and output voltage waveform

Procedure:    

Circuit is rigged up as shown in figure 1. Output voltage waveform is observed at pin 3 of the IC 555 and are traced. Capacitor voltage waveform is observed at pin 2 or 6 and are traced. Ton , Toff and T of the output waveform at pin3 are measured and verified.

Result: Astable multivibrator has been designed and tested. Parameters Frequency Duty cycle

Dept ECE, GMIT, Davangere

Theoretical value

Practical value

Page 2

LIC & AC Lab Manual

CBCS Scheme

15ECL48

Monostable Multivibrator Aim: To Design a Monostable Multivibrator using a IC555 Timer to generate a square wave of desired pulse width.

Components Required: Sl No 1 2 2 3 4 5 6 7 8

Components IC555 Resistors Capacitors DRB DC Supply CRO Bread Board CRO Probes Connecting Wires

Specification 36.36 K Ω 0.1 µF, 0.01 µF -

Quantity 1 1 1 each 1 1 1 1 2 1 set

Theory: Circuit Diagram:

Figure 1: Monostable Multivibrator

Dept ECE, GMIT, Davangere

Page 3

LIC & AC Lab Manual

CBCS Scheme

15ECL48

Circuit Design: Given pulse width W = 4 msec

Choose C=0.01µF

Waveforms:

Figure 2: Multivibrator output waveform

Procedure:    

Connections are made as shown in the circuit diagram. Trigger pulses are applied at the input pin no 2( The duty cycle of trigger pulses is adjusted so off time is less than pulse width) The pulse width of the waveforms at pin 3 is measured and verified with the desired value.. Capacitor voltage waveforms are observed at pin 2 or 6.

Result: Pulse width given W= 4 m sec Pulse width observed W=

Dept ECE, GMIT, Davangere

Page 4