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ECE 201 Circuit Theory I 1 Voltage and Current Sources Circuit Symbols Vbattery 12 V Isource 1 A

Voltage and Current Sources Circuit Symbols

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Voltage and Current Sources Circuit Symbols. IDEAL voltage source maintains the prescribed voltage across its terminals regardless of the current drawn from it. IDEAL current source maintains the prescribed current through its terminals regardless of the voltage across those terminals. - PowerPoint PPT Presentation

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Page 1: Voltage and Current Sources Circuit Symbols

ECE 201 Circuit Theory I 1

Voltage and Current Sources

Circuit Symbols

Vbattery12 V

Isource1 A

Page 2: Voltage and Current Sources Circuit Symbols

ECE 201 Circuit Theory I 2

“IDEAL” or “Independent” Sources

• IDEAL voltage source– maintains the

prescribed voltage across its terminals regardless of the current drawn from it

• IDEAL current source– maintains the

prescribed current through its terminals regardless of the voltage across those terminals

Vs12 V

LOAD

Z=A

+jB

LOADCurrent

DC 1e-009Ohm

0.012 A+ -

LOAD

Z=A

+jB

Is1 A

LOADVoltageDC 1MOhm 999.001 V

+

-

Page 3: Voltage and Current Sources Circuit Symbols

ECE 201 Circuit Theory I 3

“Controlled” or “Dependent” Sources

• A voltage or current source whose value “depends” on the value of voltage or current elsewhere in the circuit

• Use a diamond-shaped symbol

Vs1 V/V Vs=uVxVx

+

-

+

-

Page 4: Voltage and Current Sources Circuit Symbols

ECE 201 Circuit Theory I 4

Voltage-Controlled Voltage Source VCVS

• Vs is the “output” voltage

• Vx is the “reference” voltage

• u is the “multiplier”

• Vs = uVx

Vs1 V/V Vs=uVxVx

+

-

+

-

Page 5: Voltage and Current Sources Circuit Symbols

ECE 201 Circuit Theory I 5

Current-Controlled Voltage Source CCVS

• Vs is the “output” voltage

• Ix is the “reference” current

• p is the multiplier

• Vs = pIx

Vs1 Ohm Vs=pIx

-

+

Ix

Page 6: Voltage and Current Sources Circuit Symbols

ECE 201 Circuit Theory I 6

Voltage-Controlled Current Source VCCS

• Is is the “output” current

• Vx is the “reference” voltage

• a is the multiplier

• Is = aIx

Is1 Mho Vx

+

-

Is = aVx

Page 7: Voltage and Current Sources Circuit Symbols

ECE 201 Circuit Theory I 7

Current-Controlled Current Source CCCS

• Is is the “output” current

• Ix is the “reference” current

• b is the multiplier

• Is = bIx

Is1 A/A Ix Is=bIx

Page 8: Voltage and Current Sources Circuit Symbols

ECE 201 Circuit Theory I 8

Common-Emitter Transistor Amplifier

Q1

2N2222A

R11kOhm

R247kOhm

Rcollector3.3kOhm

Remitter560 Ohm

VCC

12V

BASE

COLLECTOR

EMITTER

Cc1

1uF

Cc2

1uF

Rload1kOhm

V1

1 V 1kHz 0Deg Ce

1uF

Page 9: Voltage and Current Sources Circuit Symbols

ECE 201 Circuit Theory I 9

The transistor and its equivalent circuit

Q

2N2222ABASE

COLLECTOR

EMITTER

I11 A/A

rbe

1kOhm COLLECTOR

EMITTER

BASE

Page 10: Voltage and Current Sources Circuit Symbols

ECE 201 Circuit Theory I 10

Substituting the equivalent circuit for Q1

R11kOhm

R247kOhm Rcollector

3.3kOhm

Remitter560 Ohm

VCC

12V

BASECOLLECTOR

EMITTER

Cc1

1uF

Cc2

1uF

Rload1kOhm

V1

1 V 1kHz 0Deg Ce

1uF

BETAib50 A/A

rbe

1kOhm

ib --->

Page 11: Voltage and Current Sources Circuit Symbols

ECE 201 Circuit Theory I 11

Active and Passive Elements

• Active element– a device capable of

generating electrical energy

• Voltage source• Current source• Power source

– Batteries– Generators

– a device that needs to be powered (biased)

• transistor

• Passive element– a device that absorbs

electrical energy• Resistor• Capacitor• Inductor• motor• light bulb• heating element