ELECTRONIC ENGINEERING LAB: Common-Emitter BJT Amplifier-

OBJECTIVE: To study and measure the characteristics of a common-emitter amplifier.

PROCEDURES:  

Part 1: Transistor Biasing

Using the experimental chassis given connect the DC supply as required. Use only the first stage amplifier.

(a) Calculate and measure all quiescent voltages.

(b) Simulate the circuit.

(c) Compare the calculated, simulated and measured values.

(d) Calculate and measure the emitter current and hence determine the dynamic resistance re of the amplifier.

(e) Calculate the value of β from your measured quantities.

Part 2: Common-Emitter AC Voltage Gain

(a) Calculate the amplifier voltage gain for a fully bypassed emitter using Eq. 1.2.

 (b) Apply a sinusoidal input signal, at f = 1 kHz. Observe the output waveform on the scope to be sure that there is no distortion (if there is, reduce the input signal or check the DC bias). Choose a suitable input signal voltage. Measure V_i. Measure the resulting output signal voltage, V_o using the scope.

(c) Calculate the circuit no-load voltage gain using measured values.

(d) Compare the measured value of A. with that calculated in step 2(a).

(e) Remove the bypass capacitor and measure the voltage gain of the amplifier.  

Part 3: Frequency Response

(a) Connect the amplifier as required. For a suitable input of V_sig at a frequency of f = 1 kHz, observe and measure V_o.

(b) Keeping V_sig constant vary the frequency of the signal generator and measure V_o at various frequencies. (Note: make more measurements when V_o starts to decrease at both low and high frequencies).

(c) Plot a graph of 20 log V_o/V_i using a log linear paper.

Attachment:- LAB.rar