EEGR2111 L4

Independent Sources

Voltage or current source

Independent voltage source

Ideal

Creates voltage between the two terminals REGARDLESS of external circuit

So: voltage is always known

But: the current is free to vary depending on external circuit

Independent current source

Ideal

Creates current trough the two terminals REGARDLESS of external circuit

So: current is always known

But: the voltage is free to vary depending on external circuit

Open/Short circuit

Short: no voltage drop across terminals

Open: no current through terminals

Models: as sources or resistors

Meters again

Ideally - dont disturb the circuit

So: ammeters - short circuit

So: voltmeters - open circuit

Dependent Sources

Voltage or current source

Dependent voltage source

Ideal

Creates voltage between the two terminals DEPENDENT on some current or voltage in the external circuit

VCVS - voltage-controlled voltage source

CCVS - current-controlled voltage source

So: voltage is always known

But: the current is free to vary depending on external circuit

Dependent current source

Ideal

Creates current trough the two terminals DEPENDENT on some current or voltage in the external circuit

VCCS - voltage-controlled current source

CCCS - current-controlled current source

So: current is always known

But: the voltage is free to vary depending on external circuit

Example L4-1:

Circuit (model of a BJT amplifier):

Find the voltage gain Vo / Vi

Find the power gain when the input power is defined as the power supplied by the source and the output power is defined as the power delivered to the load resistor RL

Is it possible to have voltage gain > 1 when power gain is less than 1? Explain.

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