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Circuit Theorems

A source transformation allows us to replace a voltage source and series resistor by a current source and parallel resistor. Doing so doesn't change the current or voltage.

Superposition says that the response of a linear circuit to several inputs working together is equal to the sum of the responses of each of the inputs separately.

Thévenin's theorem allows us to replace part of a circuit by a voltage source and series resistor without changing the element current or voltage.

Norton's theorem allows us to replace part of a circuit by a current source and parallel resistor, without changing current or voltage of any element.

The maximum power transfer theorem describes the condition under which one circuit transfers as much power as possible to another.

Practical Voltage Source

A PVS can often be modeled as a Thevenin circuit. This consists of a voltage souce (Voc) "open circuit voltage", in series with the Thevenin resistance.

Practical Current Source

A practical current source can often be modeled as a Norton circuit. This consists of an independent current source (isc) "short circuit current" in parallel with the Thevenin resistance.

RT --> 0

RT --> inf

A Thevenin circuit and a Norton circuit are equivalent when their iAB - VAB diagrams are the same

The output of a linear circuit can be expressed as a linear combination of its inputs.

Linear circuit:

The circuit consists only of resistors and dependent and independent sources

The circuit inputs are the voltages of all the independent voltage sources and the currents of all the independent current sources.

The output is the voltage or current of any element of the circuit.

The output of a linear circuit due to several inputs working together is equal to the sum of the outputs due to each input working separately.

When we set all but one input to 0 the other inputs become 0-V and 0-A.

0V= short circuits

0A= open circuits

Thevenins Theorem

Introduction

Source Transformations

Superposition