ECE 3111 Lab 11: Discrete BJT amplifier characteristics
1 Using a 5-V power supply, design a BJT amplifier using the circuit below. First, choose
RC and RB to provide a DC emitter current of about 0.5 mA and VCE ~ 3V. Use an npn
2N2222A transistor (in the BJT_NPN library of Multisim) or something similar. The
2N2222A has a nominal β = 220.
To choose RC and RB, write two voltage loops, from VCC to ground across the transistor,
and another from VCC to ground through RB. You will have two equations with two
unknowns, RC and RB which you can solve for.
2 Using 1F capacitors, capacitively connect an ac source vs with a 0 V offset, a small
amplitude, say 0.1V, at 1kHz, and Rs = 100K to the base of the transistor. Also
capacitively couple a load resistor RL = 1k to the collector.
Then, graphically measure the following ac quantities (this circuit will not produce a
high gain):
Av = vout/vs, where vout = vs
Rin = vin /iin does not include Rs
Rout = vout /-iout (replace load resistor with ac source and measure current leaving the +
terminal of the source, vs should be 0.)
3 Compare the simulated values to theoretical values