Sonsivri
 
*
Welcome, Guest. Please login or register.
Did you miss your activation email?
April 25, 2017, 02:56:50 02:56


Login with username, password and session length


Pages: [1]
Print
Author Topic: Astable multivibrator  (Read 4681 times)
0 Members and 1 Guest are viewing this topic.
ali.h
Newbie
*
Offline Offline

Posts: 15

Thank You
-Given: 7
-Receive: 0


« on: January 16, 2008, 12:07:28 12:07 »

Hi.
a simulation with ORCAD and PROTEUS for Astable multivibrator.
you acn change RB1,2 and/or C1,2 and see its effect on output frequency.

until c1=c2 , RB1=RB2  output is square.(T=2PW=2SW)

f=1/T=1/PW

PW=RB.C.ln2  (approximately)

           
LINK:   http://rapidshare.com/files/82187869/Astable-simulations.zip.html
Logged
leonardoaraujo.santos
Newbie
*
 Muted
Offline Offline

Posts: 10

Thank You
-Given: 0
-Receive: 3


« Reply #1 on: January 24, 2008, 06:21:42 18:21 »

Hi ali... I'm just starting with electronics.. And have some problems simulating a Astable multivibrator that actually works on my board.
Do you know if I must configure my Multisim application to simulate oscilators?
Logged
ali.h
Newbie
*
Offline Offline

Posts: 15

Thank You
-Given: 7
-Receive: 0


« Reply #2 on: January 25, 2008, 01:32:29 13:32 »

Hi.
In simulation cause of symmetry in circuit both of transistors will be in saturation state.and oscillation will not be created.
In simultion you can use a pulse generator for holding emitter of one of the transistors in VCC voltage for a short time (for example 10us).by this way you turn off a transistor and the other is on (and in saturation mode).
for pulse source sw should be very greater than pw.
for example : pw=10us  sw=10s.
In 10us value of pulse is VCC and for 10s value should be 0(GND).
Therefore after 10us the emmiter is grounded and circuit return to its actual state. and Pulse source will have no extra effect in circuit just will provide ground for emitter.
Attention: in Astable multivibrator we dont need any source( just DC power supply is needed) but in simulation for deleting effect of symmetry in circuit we have used pulse source.
In actual circuit if we obsrve saturation in both of transistors we can connect base of one the transistors to GND for moments, it caused to turning off this transistors.
If you use ORCAD you should tick "skip the initial transient bias point calculation"  option.

best regards.
Logged
localcrack
Active Member
***
Offline Offline

Posts: 168

Thank You
-Given: 62
-Receive: 20



« Reply #3 on: January 29, 2008, 09:26:55 21:26 »

In proteus you must define initial conditions (via an IC=xxx label on a wire) so as to establish an initial
state - without this the circuit is totally symmetrical
and will not oscillate.

please check the proteus sample Ff.DSN for more details.

Logged
Pages: [1]
Print
Jump to:  


DISCLAIMER
WE DONT HOST ANY ILLEGAL FILES ON THE SERVER
USE CONTACT US TO REPORT ILLEGAL FILES
ADMINISTRATORS CANNOT BE HELD RESPONSIBLE FOR USERS POSTS AND LINKS

... Copyright 2003-2999 Sonsivri.to ...
Powered by SMF 1.1.18 | SMF © 2006-2009, Simple Machines LLC | HarzeM Dilber MC