Semiconductor Fundamentals Unit 2 – Diodes and Half-Wave Rectification
Exercise 2 – Half-Wave Rectification
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to demonstrate how a diode functions
as a half-wave rectifier by using a typical half-wave rectifier circuit. You will verify your results
with an oscilloscope and a multimeter.
DISCUSSION
- Half-wave rectification converts an ac output to a pulsating dc output. The circuit consists of
a diode and a load resistance. - Either positive or negative pulsating dc output can be produced, depending on the way the
diode is connected to the circuit. - Rectification is the process of converting ac to dc. Half-wave rectification occurs when
conduction is for only one half of every ac cycle. - Dc output can be significantly lower than the ac input since the forward voltage drop of the
diode must be reached before conduction occurs and voltage appears across the load. - Half-wave rectification will be observed on an oscilloscope. Oscilloscope voltage
measurements are peak-to-peak; therefore, the following conversion factor is used to convert
the observed voltages to rms or average values.
For average voltage Vo(avg) = 0.318 x Vo(pk)
For rms voltage Vo(rms) = 0.707 x Vo(pk) - These conversion factors are for the full half-cycle, so the calculated value will be less than
the value measured with a multimeter. - Variations in the pulsating dc output of a half-wave rectifier are referred to as ripple.
- Half-wave voltage rectifiers have ripple that is the same frequency as the input voltage
frequency. - The reverse recovery time (tRR) of the diode can have an adverse affect on the output of a
half-wave rectifier at frequencies larger than 1 kHz. Reverse recovery time causes an output
voltage pulse in a direction opposite that of the normal half-wave pulse.