ECE 2212

EXPERIMENT 9

30 March 2017

Bipolar Junction Transistor (BJT) Common-Emitter Amplifier

COMPONENTS

2N3904 or 2N2222 npn transistor

Resistors: 5kW, 100kW, others as needed.

Capacitors: 1 or 10 microfarad as needed.

Note: Use the 2N3904 or 2N2222 npn transistor device models in SPICE rather than the default model

DC Bias Analysis

Construct the circuit in Figure 9.1. Use V_CC = 10 volts. Adjust R3 such that your Q-Point for VCEQ and ICQ are in the center third of the DC Load Line. Measure Q-Point values for IBQ, VCEQ, and ICQ. Be sure you measure the actual resistor values for your measurement to obtain more accurate results. Compare your results with a SPICE analysis of this circuit. Vs should be turned off for the DC analysis. This DC circuit is similar to the circuit in Experiment 8. Watch the polarities on the electrolytic capacitors. Positive terminal to the base and the other positive terminal to the collector.

Figure 9.1

Amplifier Operation

Now measure the voltage gain defined by Av=vout/vs. Use a 1 kHz sinusoidal input for Vs and change the amplitude as necessary to obtain a sinusoidal voltage output. Also look at the transfer characteristic. Compare with a SPICE analysis. The voltage gain is computed from Av = -gm(Rc||RL) and gm=ICQ/VT where VT = kT/q approximately 25.8 mV at 300K.