EE 321 Lab

The purpose of this lab is design and test a two-stage BJT amplifier.

For this lab keep records in your notebook as you have been. Your notebooks will be graded as usual, but later. Do not hand in the notebook but use it to write a formal lab report a week later. The report should be typed or computer printed. Include an introduction, design, design choices and decisions, hand analysis, spice analysis, tests, results, and conclusion.

Design a capacitor-coupled two stage amplifier. Both stages will be common-emitter amplifier. The output should not respond to DC changes at the input.  Use + 15 and -15 V power supplies. The input will be your digital signal generator with an source resistance of 10 k (added in series). vin is at the junction of the 10 k and the signal generator. Measure the output with a load of  10 k. The output voltage swing must be linear to at least 6 V p-p, and the gain (vout/vin) must between 150 and 200 V/V (with the source and load resistance in place). Use 2N3904's (npn) and/or 2N3906's (pnp) (both are rated at 100 mA and 40 V reverse breakdown).

Before coming to lab analyze your design, finding the bias voltage at each node, the gain, Rin and Rout. This will save lots of time.

If possible do a Pspice analysis of the circuit.

Build and test the amplifier. Measure the dc voltages that determine the bias conditions. These should agree with your calculated values.

Measure the gain at 1 kHz and 10 kHz.

Measure Rin and Rout as you did in lab #9.

Extra credit. Use a current mirror for the bias (Figure 4.42 in Sedra and Smith). Add a 1 k in series with each emitter.

© Copyright 2000 New Mexico Institute of Mining and Technology