ECE 32B LAB MANUAL

ECE 32B/32F: Electronic Circuit Analysis & DesignLab ManualNovember 20141ECE 32B: Electronic Circuit Analysis & Design LabBipolar Junction TransistorBipolar junction transistor(BJT) is a type oftransistorthat relies on the contact of two types ofsemiconductor for its operation. Naming of BJT: Bipolartransistorsare so named because their operation involves bothelectronsandholes. Charge Carriers: These two kinds of charge carriers are characteristic of two kinds of doped semiconductor material; - Electrons are majority charge carriers in n-type semiconductors, - Holes are majority charge carriers in p-type semiconductors.

November 2014ECE 32B: Electronic Circuit Analysis & Design Lab2NPN Transistor AmplifierNovember 2014ECE 32B: Electronic Circuit Analysis & Design Lab3

Output CharacteristicsNovember 2014ECE 32B: Electronic Circuit Analysis & Design Lab4

Output Characteristic Curve relates output collector current, (Ic) collector voltage, (Vce) for different values of base current, (Ib). Load Line: At this point, transistor current is maximum and voltage across collector is minimum, for a givenload .Load line shows all possible operating points when different values of base current are applied. It is necessary to set the initial value ofVcecorrectly to allow the output voltage to vary both up and down when amplifying AC input signals. Operating Point, or Quiescent Point,Q-point: This is called setting of the operating point orQuiescent Point,Q-point..Load LineNovember 2014ECE 32B: Electronic Circuit Analysis & Design Lab5

Experiment# 1 Frequency Response of an AmplifierFrequency Response: Relationship between GAIN and FREQUENCY

(Gain)dB =

FrequencyGainNovember 20146ECE 32B: Electronic Circuit Analysis & Design LabSemi-log paperPractical Frequency ResponseNovember 2014ECE 32B: Electronic Circuit Analysis & Design Lab7

Frequency RangeFrequency Range:- LOW Frequencies: At low frequencies, capacitive reactance XC is large and series capacitors develop voltage drop and reducesgain.- HIGH frequencies: At high frequencies, capacitive reactance XC is small, and parallel capacitors short out transistor and load. - MID frequencies: This is a region between the high and low frequencies. The gain is generally constant and is at a maximum for the circuit.November 20148ECE 32B: Electronic Circuit Analysis & Design Lab

Bandwidth/Roll-off of AmplifierBreak Points: The points at which the gain drops to 3 dB below the mid-frequency gain are called the break-points.Bandwidth: The difference between the breakpoint frequencies is the bandwidth of the amplifier.November 20149ECE 32B: Electronic Circuit Analysis & Design Lab

Break pointsRoll-off RateRoll-off Rate: Rate at which gain decreases from the mid-frequency value. The steeper the drop, the greater the roll-off.dB/decade: Gain decrease where the two frequencies differ by a factor of TEN. dB/octave: Gain decrease where the two frequencies differ by a factor of TWO.

November 201410ECE 32B: Electronic Circuit Analysis & Design Lab

Frequency Response Factors Factors Affecting Frequency Response:- Capacitance in circuit- Gain of circuit- Transistor characteristics itself. Transfer characteristic ICE/IBE. Input characteristic IBE/VBE . Output characteristic VCE/IEENovember 201411ECE 32B: Electronic Circuit Analysis & Design Lab