ECE 201 Circuit Theory I1 Voltage and Current Sources Circuit Symbols

ECE 201 Circuit Theory I2 “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

ECE 201 Circuit Theory I3 “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

ECE 201 Circuit Theory I4 Voltage-Controlled Voltage Source VCVS V s is the “output” voltage V x is the “reference” voltage u is the “multiplier” V s = uV x

ECE 201 Circuit Theory I5 Current-Controlled Voltage Source CCVS V s is the “output” voltage I x is the “reference” current p is the multiplier V s = pIx

ECE 201 Circuit Theory I6 Voltage-Controlled Current Source VCCS I s is the “output” current V x is the “reference” voltage a is the multiplier I s = aIx

ECE 201 Circuit Theory I7 Current-Controlled Current Source CCCS I s is the “output” current I x is the “reference” current b is the multiplier I s = bIx

ECE 201 Circuit Theory I8 Common-Emitter Transistor Amplifier

ECE 201 Circuit Theory I9 The transistor and its equivalent circuit

ECE 201 Circuit Theory I10 Substituting the equivalent circuit for Q1

ECE 201 Circuit Theory I11 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