EE210 Circuit Laboratory II
2018-2019
EXPERIMENT 1
SEMICONDUCTOR JUNCTION DIODES
1.1 Objectives
In this experiment,
1. The v - i characteristics of silicon and germanium diodes are investigated
2. Several diode circuits are designed.
3. The performances of several diode circuits are determined.
1.2 Equipment List
1. Signal Generator, DC Power Supply, Multi-meter,
2. Diodes (1N4007, BA159, AA 143),
3. Resistors (100, 1K).
1.3 Preliminary Work
1) Study semiconductors from ‘Notes on Semiconductor Diodes’ document.
2) What is “hysteresis effect”?
3) Plot on graph paper the v – i characteristics of silicon and germanium diodes. Explain the
required parameters to plot graph shortly A common piecewise linear model for a junction
diode is given in Fig.-1.
Figure-1
EE210 Circuit Laboratory II
2018-2019
1.5 Experimental Procedure
1) A quick way of determining whether a diode is defective or not is to use an ohmmeter. If the
internal battery of the ohmmeter forward biases the pn junction, a low resistance is read on the
scale, otherwise, a high resistance is read. If the diode is defective, the ratio of the two
readings is close to unity (poor rectification). Prior to proceeding with the experiment, using
the ohmmeter method, test your diodes for defectiveness and determine their anodes. Which
terminal does the band on the diode indicate, anode or cathode?
2) Set up the circuit in Fig.-2 to display the v – i characteristics of different types of silicon and
germanium diodes available.
Figure-2
a. Set CH1 and CH2 input couplings of oscilloscope to DC. Use 100  resistor and sketch
the v – i curves for all diodes. Also determine the parameters of the piecewise linear model
for the diodes (i.e., rf, rr and Vo).
b. Increase the resistance to 1 k, frequency to 10 kHz and observe the hysteresis effect on
the v – i characteristics. Draw only a typical one. Considering the hysteresis effect, explain
what is meant by “switching” or “high speed” diode.