Principle Function Of Operation Amplifiers

  The page will make only one statement about Operation Amplifiers, which is:

  An operational amplifier, when used as an amplifier, will do everything it can to keep the voltage at the PLUS input equal to the voltage at the MINUS input.

  That is to say that if the voltage at one of the inputs is increased or decreased the amplifier will adjust its output voltage so that the voltage at the other input is the same as the first. This will be true for inverting and non-inverting amplifiers.

  The following diagram gives three examples of this principle.


  In general terms, the 'feedback' resistor network between the OUTPUT and the MINUS inputs acts as a voltage divider that proportions the amount of feedback and thereby determines the theoretical gain of the amplifier.

  By selecting resistors, capacitors and other components, the above principle can be used to perform a wide variety of amplifying or attenuating functions.

  The following are two, single power supply amplifier circuits that can be used to test the statement made previously.