What is bistable multivibrator.And where it is used?

Question

What is bistable multivibrator.And where it is used?

Answer 1

A bistable multivibrator, also known as a flip-flop, has an output which can be in one of two states, logic 0 and logic 1. The key thing is that it is stable in either state, ie. unless you do something to its inputs its output will stay the same.

The inputs may be "set" and "reset". A pulse on these inputs changes the output to a logic 1 or logic 0 respectively. This is also called a SR flip-flop.

Alternatively, it may have a single "clock" or "trigger" input, when it receives a pulse it changes state from 0 to 1 or 1 to 0.

Other varieties of multivibrator are:

Monostable - always returns to its resting state after a fixed delay.

Astable - flips between states constantly (ie. it's an oscillator)

Here are some circuits using the well known 555 timer IC:

http://www.kpsec.freeuk.com/555timer.htm

Answer 2

Take 2 (old fashioned) transistors and make two standard emitter-couled amplifiers. Connect them back to back with the output of one to the input of the other. It should both be capacitor coupled. As one is fully in conduction mode (collector high) the other's input (base) is low so it doesn't conduct. This state continues. Both bases are connected to a triggering pulse, that sets of change in state. The one that was not conducting switches to conducting state & vice versa. Till the next trigger pulse appears this state is also stable. This bistable device is the elemental circuit to store one of the two binary states and hence the name. The state '0' or '1' is assigned by one of the collectors going high (transistor not conducting) or not. It is also called a 'flip-flop'.

An array of such devices is used to write and store a string of binary digits (0 and 1s) and is called a 'register' that is the basic memory unit in digital circuitry that make up a computer.

Answer 3

A multivibrator is  a form of oscillator that makes square waves.

an Austable multivibrator is a form that has no stable states, so it constantly flips from one state to the other (eg 0 and 5 volts).  An NE555 ic can be configured to do this

A monostable multivibrator has one stable state, so when you activate it, it turns on, and then turns off again, where it is stable (you have to activate it again to turn it on again).  the on time can be varied, and a monostable multivibrator can act like a timer.  An NE 555 timer can be configured to do this too.

A bistable multivibrator has two stable states, ie, activate it, and it will flip its 'switch, and hold it there untill you activate it again.  This circuit is sometimes called a flipflop.  a basic use is to divide the frequency of a pulse chain by two.