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, through feedback, to keep the voltage at the MINUS input the same as the voltage at the PLUS 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.

  None of the example circuits shown on this page have been tailored for an actual application. For OPAMP circuit design considerations, consult the datasheet for the device being used.

Using An OPAMP As A Comparator

  If there are Operational Amplifiers left over in a circuit and a Comparator is needed one can be created by adding a diode or transistor to the amplifiers output depending on the current capacity required.

Comparator Made From An Operational Amplifier

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Please Read Before Using These Circuit Ideas

  The explanations for the circuits on these pages cannot hope to cover every situation on every layout. For this reason be prepared to do some experimenting to get the results you want. This is especially true of circuits such as the "Across Track Infrared Detection" circuits and any other circuit that relies on other than direct electronic inputs, such as switches.

  If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.

  Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.

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16 March, 2011