Lab Report 9
Diodes and Rectifiers
Jeffery Olson
March 19th, 2025
1. Introduction
Diodes are fundamental semiconductor devices that allow
current to flow in one direction while blocking it in the
opposite direction. This unidirectional behavior makes
them essential in applications such as rectification, signal
clipping, and voltage regulation. When a diode is forward
biased, it permits current flow after reaching a threshold
voltage (~0.7V for silicon diodes). In reverse bias, the
diode ideally blocks current, except for a negligible
leakage current. The ability of diodes to convert
alternating current (AC) into direct current (DC) is crucial
in power supply circuits. This experiment explores these
characteristics by measuring I-V curves and
implementing a rectifier circuit to demonstrate AC-to-DC
conversion.
2. Theory
The current through a diode is governed by Shockleyโs
diode equation:
๐ผ๐ผ=๐ผ๐ผ๐ ๐ (exp ๏ฟฝ๐๐
๐๐๐๐๐๐๏ฟฝโ1)
where:
I is the current through the diode,
V is the voltage across the diode,
๐ผ๐ผ๐ ๐ is the reverse saturation current,
๐๐๐๐ is the thermal voltage (~0.025V at room temperature),
and
n is the non-ideality factor (typically 1-2).
For rectification, diodes are arranged in half-wave or full-
wave configurations. A half-wave rectifier allows only
one half of the AC waveform to pass, while a full-wave
rectifier utilizes both halves, often employing a bridge
configuration for efficiency. The introduction of a
capacitor smooths the rectified output by storing charge
and reducing ripple voltage, improving the quality of the
DC output.
4. Procedure
Part 1: Forward and Reverse Bias
Characteristics
1. Construct the circuit as shown in Figure 1.
2. Measure current through the circuit and voltage
across the diode and resistor for five supply
voltages (0-25V) in forward and reverse bias.
3. Observe that forward bias conduction starts near
0.7V, while reverse bias current remains
negligible.
Part 2: I-V Characteristics of a Diode
1. Construct the circuit as shown in Figure 2.
2. Measure and record the I-V curve:
3. 3-4 points in the near-zero current region.
