Ch 5: Handy Circuit Analysis Techniques Flashcards
Handy Circuit Analysis Techniques and Principles
covered in this chapter
Superposition
Source Transformation
Thévenin Equivalent Circuit
Norton Equivalent Circuit
Maximum Power Transfer Theorem
Delta-Wye Equivalents
Linear Circuit:
Definition
A circuit composed entirely of:
- Independent Sources
- Linear Dependent Sources
- Linear Elements
Linear Element:
Definition
A passive element that has a linear voltage-current relationship
Superposition:
Basic Idea
Remove all independent sources.
Then, apply one source at a time, calculating the resulting voltage or current values.
Finally, add the results together.
*Only applies to linear circuits.
Superposition:
Steps
- Turn off all independent sources except one. Find the output voltage or current due to that source
- Repeat for each independent source
- Find the total contribution by summing all the contributions due to the independent sources
Principle of
Superposition
The total response(desired current or voltage) of a Linear Circuit with multiple independent sources can be obtained by summing the responses caused by the separate independent sources.
Superposition:
How to turn off an Independent Current Source
Simply remove the source, replacing it with an open circuit.
Superposition:
How to turn off a Voltage Source
Take out the source, connect the two terminals.
Replaces the Voltage Source with a short circuit.
Practical Current Source
A current source model that more closely matches real world sources.
Represents the internal resistance inherent in a current source by placing a very resistance in parallel with an ideal current source.
Practical Voltage Source
A more accurate model of real voltage sources.
Represents the internal resistance of the source by placing a small resistance in series with an Ideal Voltage Source
Source Transformation:
Basic Idea
Practical Current Sources can be electrically equivalent to Practical Voltage Sources.
Source Transformation:
Equivalency Equations
A Practical Voltage Source has a Voltage Vs, and an internal resistance Rs in series with it.
The equivalent Practical Current Source has a current is and an internal resistance Rp in parallel with it.
For these to be equivalent:
Rs = Rp
vs = Rpis = Rsis
is = vs/Rs
Source Transformation:
Important Points
(8)
- Common goal:
- End up with all current sources or all voltage sources
- Can be used repeatedly to simplify a circuit
- Resistor value stays the same, but is NOT the same resistor. Currents and Voltages associated with the resistor are lost
- If the resistor’s voltage or current controls a dependent source, it should NOT be used in source transformation
- If the resistor’s voltage or current is of interest, it shouldn’t be used in source transformation
- The head of the current source corresponds to the positive terminal of the voltage source
- To transform a voltage source: needs resistor in series
- To transform a current source: needs a resistor in parallel
Source Transformation:
Transforming a Voltage Source
to a Current Source
For a resistor, R, in series with the voltage source, vs,
Replace the voltage source with current source, is,
where is = vs / R
and place the resistor in parallel with it.
Source Transformation:
Transform a Current Source
to a Voltage Source
For a Current Source, is, in parallel with a resistor, R,
replace both with a Voltage Source, vs,
where vs = isR
Place the resistor in series with the voltage source.