ECE 2212

EXPERIMENT 7

15 November 2012

Bipolar Junction Transistor (BJT) Measurements, Circuit Analysis, And Amplifier Operation

COMPONENTS

2N3904 or 2N2222 npn transistor

Resistors: 5kW and 100kW

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 1. Use = 10 Volts for the DC supply. Measure and record the Q-Point values of I_B, I_C, V_BE, and V_CE. One of many measurement approaches is to measure the voltage across the RB and RC resistors to obtain the current rather than inserting an ammeter in series. 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. Use the 2N3904 or 2N2222 in the SPICE library. The signal source v_in(t) should be set to zero for this portion of the experiment. You may have to adjust V_GG = 1.5 volts to obtain a Q-Point in the forward-active region because of the potentially wide variation of BJT β values.

Demonstrate Small-Signal and Large-Signal Operation

Now set v_in(t) for a 1 kHz sine wave from the function generator. Adjust the amplitude initially

to 0.5 Volts (1 V_Peak-to-Peak), Measure the voltage gain. Simulate the circuit in SPICE with your transistor using a transient analysis. Explain your results in the context of a load-line analysis. Use the small-signal model to compute the voltage gain. Also show the transfer characteristic. Adjust v_in(t) to demonstrate clipping.

Another math joke if can handle it!

Another upgrade to IE 9 and I suppose I will also upgrade to a bug-filled Windows 8. This Dilbert cartoon expresses my feelings about software upgrades!