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Anglicky v odbornch pedmtech"Support of teaching technical subjects in EnglishTutorial: Mechanic electrician

Topic: Electronics II.class Operational Amplifiers: Inverting Amplifiers Part 1 - EquationsPrepared by: Ing. Jaroslav Bernkopf

Projekt Anglicky v odbornch pedmtech, CZ.1.07/1.3.09/04.0002je spolufinancovn Evropskm socilnm fondem a sttnm rozpotem esk republiky.

1Definition:

An inverting amplifier is a circuit, which increases a voltage while inverting its polarity.

See the example in the figure below:

The input voltage is only 1 V, while the output voltage is 10 V.

The input voltage is positive, while the output is negative. Operational AmplifiersInverting Amplifiers Part 1 - Equations

+1 V-10 V2

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-1 V+10 VDescription:

The output polarity of an inverting amplifier is reversed as compared to its input.

If the input voltage is positive, the output voltage is negative, and vice versa.Operational AmplifiersInverting Amplifiers Part 1 - Equations

+1 V-10 VInput positive, output negativeInput negative, output positive3

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Operational AmplifiersInverting Amplifiers Part 1 - Equations4

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Inverting Amplifiers Part 1 - EquationsOperational AmplifiersR2 is on the top, therefore The higher ..., the higher ...R1 is on the bottom, therefore The higher ..., the lower...5

5Virtual Ground

We call the node between R1, R2, and V- Virtual ground.It keeps its ground potential without being directly connected to the ground.The negative feedback ensures that the voltage difference between the inputs V+ and V- is zero.

There is no voltage, no signal in this node.

Operational AmplifiersInverting Amplifiers Part 1 - EquationsV+V-Virtual ground6

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Operational AmplifiersInverting Amplifiers Part 1 - EquationsV+V-Rin10k7

7Task

See the figure below.Given the values of R1, R2, and V1, determinethe polarity and the value of the output voltage V2the input resistance Rin Operational AmplifiersInverting Amplifiers Part 1 - EquationsV+V-

22k100kV1 = -1.3 V 8V2 = ?

8Operational AmplifiersInverting Amplifiers Part 1 - Equations

22k100kV1 = -1.3 V 9V2 = +5.91 V

9Operational AmplifiersInverting Amplifiers Part 1 - Equations

22k100kV1 = -1.3 V 10Rin = 22kV2 = +5.91 V

10Operational AmplifiersInverting Amplifiers Part 1 - EquationsReferences

http://www.wikipedia.comhttp://www.thefreedictionary.com11

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