Semiconductor Fundamentals Unit 4 – Diode Wave Shaping and Zener Regulation
Exercise 1 – Diode Wave Shaping
EXERCISE OBJECTIVE
When you have completed this exercise, you will be able to demonstrate limiting and clamping
by using diode circuits. You will verify your results with an oscilloscope.
DISCUSSION
- Limiter or clipper circuits remove positive and/or negative portions of a waveform. Sine
waves can be converted to a rectangular wave using a limiter. - Diode limiters are classified as series or parallel.
- Series diode limiters, shown in this exercise are half-wave rectifiers.
- Parallel diode limiters are composed of a series resistor, diode and load resistance in parallel
with the diode. When the diode is forward biased the output is limited to the diode forward
voltage. The half-cycle input voltage appears at the output when the diode is reversed bias. - A limiting circuit with a variable voltage bias at the diode is illustrated in this exercise. The
point where limiting occurs is controlled by the amount of bias added to the circuit by a
positive variable voltage supply. - Clamping circuits shift the unwanted positive or negative portions of an input waveform to a
different output dc voltage reference level. - Clamping circuits are also referred to as restorers or baseline stabilizers.
- Clamping circuits with capacitors must have short charge time constants and long discharge
time constants compared to the period of the input signal or the output waveform will be
distorted.