3: Nodal Analysis, Study notes of Law

The aim of nodal analysis is to determine the voltage at each node relative ... simultaneous equations to solve. ... Current sources cause no problems.

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3: Nodal Analysis
3: Nodal Analysis
Aim of Nodal Analysis
Nodal Analysis Stage 1:
Label Nodes
Nodal Analysis Stage 2:
KCL Equations
Current Sources
Floating Voltage Sources
Weighted Average Circuit
Digital-to-Analog
Converter
Dependent Sources
Dependent Voltage
Sources
Universal Nodal Analysis
Algorithm
Summary
E1.1 Analysis of Circuits (2017-10216) Nodal Analysis: 3 1 / 12
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3: Nodal Analysis

Aim of Nodal Analysis Nodal Analysis Stage 1: Nodal Analysis Stage 2: Current Sources Floating Voltage Sources Weighted Average Circuit Digital-to-Analog Dependent Sources Dependent Voltage Universal Nodal Analysis Summary

Nodal Analysis: 3 – 1 / 12

Aim of Nodal Analysis

Aim of Nodal Analysis Nodal Analysis Stage 1: Nodal Analysis Stage 2: Current Sources Floating Voltage Sources Weighted Average Circuit Digital-to-Analog Dependent Sources Dependent Voltage Universal Nodal Analysis Summary

Nodal Analysis: 3 – 2 / 12

The aim of nodal analysis is to determine the voltage at each node relativeto the reference node (or ground). Once you have done this you can easilywork out anything else you need.

Aim of Nodal Analysis

Aim of Nodal Analysis Nodal Analysis Stage 1: Nodal Analysis Stage 2: Current Sources Floating Voltage Sources Weighted Average Circuit Digital-to-Analog Dependent Sources Dependent Voltage Universal Nodal Analysis Summary

Nodal Analysis: 3 – 2 / 12

The aim of nodal analysis is to determine the voltage at each node relativeto the reference node (or ground). Once you have done this you can easilywork out anything else you need.There are two ways to do this:(1)

Nodal Analysis

  • systematic; always works

(2)

Circuit Manipulation

  • ad hoc; but can be less work and clearer

Reminders: A node is all the points in a circuitthat are directly interconnected.We assume the interconnectionshave zero resistance so all pointswithin a node have the samevoltage. Five nodes:

A,

· · ·

, E

.

Aim of Nodal Analysis

Aim of Nodal Analysis Nodal Analysis Stage 1: Nodal Analysis Stage 2: Current Sources Floating Voltage Sources Weighted Average Circuit Digital-to-Analog Dependent Sources Dependent Voltage Universal Nodal Analysis Summary

Nodal Analysis: 3 – 2 / 12

The aim of nodal analysis is to determine the voltage at each node relativeto the reference node (or ground). Once you have done this you can easilywork out anything else you need.There are two ways to do this:(1)

Nodal Analysis

  • systematic; always works

(2)

Circuit Manipulation

  • ad hoc; but can be less work and clearer

Reminders: A node is all the points in a circuitthat are directly interconnected.We assume the interconnectionshave zero resistance so all pointswithin a node have the samevoltage. Five nodes:

A,

· · ·

, E

.

Ohm’s Law:

V

BD

=

IR

5

Aim of Nodal Analysis

Aim of Nodal Analysis Nodal Analysis Stage 1: Nodal Analysis Stage 2: Current Sources Floating Voltage Sources Weighted Average Circuit Digital-to-Analog Dependent Sources Dependent Voltage Universal Nodal Analysis Summary

Nodal Analysis: 3 – 2 / 12

The aim of nodal analysis is to determine the voltage at each node relativeto the reference node (or ground). Once you have done this you can easilywork out anything else you need.There are two ways to do this:(1)

Nodal Analysis

  • systematic; always works

(2)

Circuit Manipulation

  • ad hoc; but can be less work and clearer

Reminders: A node is all the points in a circuitthat are directly interconnected.We assume the interconnectionshave zero resistance so all pointswithin a node have the samevoltage. Five nodes:

A,

· · ·

, E

.

Ohm’s Law:

V

BD

=

IR

5

KVL:

V

BD

=

V

B

V

D

KCL:

Total current exiting any closed region is zero.

Nodal Analysis Stage 1: Label Nodes

Aim of Nodal Analysis Nodal Analysis Stage 1: Nodal Analysis Stage 2: Current Sources Floating Voltage Sources Weighted Average Circuit Digital-to-Analog Dependent Sources Dependent Voltage Universal Nodal Analysis Summary

Nodal Analysis: 3 – 3 / 12

To find the voltage at each node, the firststep is to label each node with its voltageas follows (1) Pick any node as the voltage reference. Label its voltage as

0 V

.

(2) If any fixed voltage sources are connected to a labelled node, label theirother ends by adding the value of the source onto the voltage of thelabelled end.(3) Pick an unlabelled node and label it with

X, Y,...

, then go back to

step (2) until all nodes are labelled.

Nodal Analysis Stage 1: Label Nodes

Aim of Nodal Analysis Nodal Analysis Stage 1: Nodal Analysis Stage 2: Current Sources Floating Voltage Sources Weighted Average Circuit Digital-to-Analog Dependent Sources Dependent Voltage Universal Nodal Analysis Summary

Nodal Analysis: 3 – 3 / 12

To find the voltage at each node, the firststep is to label each node with its voltageas follows (1) Pick any node as the voltage reference. Label its voltage as

0 V

.

(2) If any fixed voltage sources are connected to a labelled node, label theirother ends by adding the value of the source onto the voltage of thelabelled end.(3) Pick an unlabelled node and label it with

X, Y,...

, then go back to

step (2) until all nodes are labelled.

Nodal Analysis Stage 1: Label Nodes

Aim of Nodal Analysis Nodal Analysis Stage 1: Nodal Analysis Stage 2: Current Sources Floating Voltage Sources Weighted Average Circuit Digital-to-Analog Dependent Sources Dependent Voltage Universal Nodal Analysis Summary

Nodal Analysis: 3 – 3 / 12

To find the voltage at each node, the firststep is to label each node with its voltageas follows (1) Pick any node as the voltage reference. Label its voltage as

0 V

.

(2) If any fixed voltage sources are connected to a labelled node, label theirother ends by adding the value of the source onto the voltage of thelabelled end. (3) Pick an unlabelled node and label it with

X, Y,...

, then go back to

step (2) until all nodes are labelled.

Nodal Analysis Stage 1: Label Nodes

Aim of Nodal Analysis Nodal Analysis Stage 1: Nodal Analysis Stage 2: Current Sources Floating Voltage Sources Weighted Average Circuit Digital-to-Analog Dependent Sources Dependent Voltage Universal Nodal Analysis Summary

Nodal Analysis: 3 – 3 / 12

To find the voltage at each node, the firststep is to label each node with its voltageas follows (1) Pick any node as the voltage reference. Label its voltage as

0 V

.

(2) If any fixed voltage sources are connected to a labelled node, label theirother ends by adding the value of the source onto the voltage of thelabelled end. (3) Pick an unlabelled node and label it with

X, Y,...

, then go back to

step (2) until all nodes are labelled.

Nodal Analysis Stage 1: Label Nodes

Aim of Nodal Analysis Nodal Analysis Stage 1: Nodal Analysis Stage 2: Current Sources Floating Voltage Sources Weighted Average Circuit Digital-to-Analog Dependent Sources Dependent Voltage Universal Nodal Analysis Summary

Nodal Analysis: 3 – 3 / 12

To find the voltage at each node, the firststep is to label each node with its voltageas follows (1) Pick any node as the voltage reference. Label its voltage as

0 V

.

(2) If any fixed voltage sources are connected to a labelled node, label theirother ends by adding the value of the source onto the voltage of thelabelled end. (3) Pick an unlabelled node and label it with

X, Y,...

, then go back to

step (2) until all nodes are labelled.

Nodal Analysis Stage 2: KCL Equations

Aim of Nodal Analysis Nodal Analysis Stage 1: Nodal Analysis Stage 2: Current Sources Floating Voltage Sources Weighted Average Circuit Digital-to-Analog Dependent Sources Dependent Voltage Universal Nodal Analysis Summary

Nodal Analysis: 3 – 4 / 12

The second step is to write down a KCL equation for each node labelledwith a variable by setting the total current flowing out of the node to zero.For a circuit with

N

nodes and

S

voltage sources you will have

N

S

1

simultaneous equations to solve. We only have one variable:^ X

8

1 k

X

0

2 k

X

(

3 k

= 0

Nodal Analysis Stage 2: KCL Equations

Aim of Nodal Analysis Nodal Analysis Stage 1: Nodal Analysis Stage 2: Current Sources Floating Voltage Sources Weighted Average Circuit Digital-to-Analog Dependent Sources Dependent Voltage Universal Nodal Analysis Summary

Nodal Analysis: 3 – 4 / 12

The second step is to write down a KCL equation for each node labelledwith a variable by setting the total current flowing out of the node to zero.For a circuit with

N

nodes and

S

voltage sources you will have

N

S

1

simultaneous equations to solve. We only have one variable:^ X

8

1 k

X

0

2 k

X

(

3 k

= 0

Numerator for a resistor is always of the form

X

V

N

where

V

N

is the

voltage on the other side of the resistor.

Nodal Analysis Stage 2: KCL Equations

Aim of Nodal Analysis Nodal Analysis Stage 1: Nodal Analysis Stage 2: Current Sources Floating Voltage Sources Weighted Average Circuit Digital-to-Analog Dependent Sources Dependent Voltage Universal Nodal Analysis Summary

Nodal Analysis: 3 – 4 / 12

The second step is to write down a KCL equation for each node labelledwith a variable by setting the total current flowing out of the node to zero.For a circuit with

N

nodes and

S

voltage sources you will have

N

S

1

simultaneous equations to solve. We only have one variable:^ X

8

1 k

X

0

2 k

X

(

3 k

= 0

(

X

    • 3

X

  • (

X

    1. = 0

11

X

= 44

X

= 4

Numerator for a resistor is always of the form

X

V

N

where

V

N

is the

voltage on the other side of the resistor.

Current Sources

Aim of Nodal Analysis Nodal Analysis Stage 1: Nodal Analysis Stage 2: Current Sources Floating Voltage Sources Weighted Average Circuit Digital-to-Analog Dependent Sources Dependent Voltage Universal Nodal Analysis Summary

Nodal Analysis: 3 – 5 / 12

Current sources cause no problems.