EEE/ETI 1202
CIRCUITS & NETWORK THEORY I
LECTURE 2
1
, Voltage and Current Sources
The term voltage source is used to describe a source of energy which
establishes a potential difference across its terminals.
Most of the sources encountered in everyday life are voltage sources e.g.,
batteries, d.c. generators, alternators etc.
The term current source is used to describe a source of energy that provides
a current e.g., collector circuits of transistors.
Voltage and current sources are called active elements because they provide
electrical energy to a circuit
An ideal voltage source (also called constant-voltage source) is one that
maintains a constant terminal voltage, no matter how much current is
drawn from it.
An ideal voltage source has zero internal resistance.
2
, A real or non-ideal voltage source has low but finite internal resistance
(Rint) that causes its terminal voltage to decrease when load current is
increased and vice-versa.
An ideal current source or constant current source is one which will supply
the same current to any resistance (load) connected across its terminals. An
ideal current source has infinite internal resistance.
A real or non-ideal current source has high but finite internal resistance
(Rint). Therefore, the load current (IL) will change as the value of load
resistance (RL) changes.
A real current source can be represented by an ideal current source (I) in
parallel with its internal resistance (Rint)
3
, Voltage to current source conversion. Source Conversion
4
CIRCUITS & NETWORK THEORY I
LECTURE 2
1
, Voltage and Current Sources
The term voltage source is used to describe a source of energy which
establishes a potential difference across its terminals.
Most of the sources encountered in everyday life are voltage sources e.g.,
batteries, d.c. generators, alternators etc.
The term current source is used to describe a source of energy that provides
a current e.g., collector circuits of transistors.
Voltage and current sources are called active elements because they provide
electrical energy to a circuit
An ideal voltage source (also called constant-voltage source) is one that
maintains a constant terminal voltage, no matter how much current is
drawn from it.
An ideal voltage source has zero internal resistance.
2
, A real or non-ideal voltage source has low but finite internal resistance
(Rint) that causes its terminal voltage to decrease when load current is
increased and vice-versa.
An ideal current source or constant current source is one which will supply
the same current to any resistance (load) connected across its terminals. An
ideal current source has infinite internal resistance.
A real or non-ideal current source has high but finite internal resistance
(Rint). Therefore, the load current (IL) will change as the value of load
resistance (RL) changes.
A real current source can be represented by an ideal current source (I) in
parallel with its internal resistance (Rint)
3
, Voltage to current source conversion. Source Conversion
4
