Physics  permalink

Higher Unit 2 - Operational Amplifiers 3 - Gain

This discussion has been closed.

Messages: 1 - 1 of 1
  • Message 1. 

    Posted by BitesizePhysicsTeacher (U15165682) on Thursday, 31st January 2013

    All amplifiers have the effect of multiplying their input signals, usually to make them larger.

    The factor by which the input is multiplied is called the 'gain'.

    Gain = Voltage Output ÷ Input Voltage

    or

    Gain = V(out) / V (in)

    You will have seen this before in SG physics - www.bbc.co.uk/bitesi...

    For operational amplifiers (both inverting and differential) the gain is given by the ratio of the feedback and input resistors.

    Gain = Rf / R1

    So, for inverting mode -

    Vo = - Rf / R1 x V1

    (DON'T FORGET THE NEGATIVE - it's an INVERTING mode amplifier!)

    and for differential mode -

    Vo = Rf / R1 x (V2 - V1)

    In each case the input voltage(s) are multiplied by the gain.

    **N.B. the inverting mode op amp can be treated as a special case of the differential mode, where V2 is set to 0V -

    i.e. Vo = Rf / R1 x (V2 - V1) = Rf / R1 x (0 - V1) = - Rf/R1 x V1

    Report message1

Back to top

About this Board

The Bitesize messageboards have now closed

or register to take part in a discussion.


The message board is currently closed for posting.

The boards are now closed

This messageboard is pre-moderated.

Find out more about this board's House Rules

Search this Board

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.