4-1
CHAPTER 4
WAVE SHAPING
LEARNING OBJECTIVES
Upon completion of this chapter you will be able to:
1. Explain the operation of series-limiter circuits.
2. Explain the operation of parallel-limiter circuits.
3. Describe the operation of a dual-diode limiter circuit.
4. Explain the operation of clamper circuits.
5. Explain the composition of nonsinusoidal waves.
6. Explain how RC and RL circuits are used as integrators.
7. Explain how RC and RL circuits are used as differentiators.
8. Explain the operation of a counting circuit.
9. Explain the operation of a step-by-step counter used as a frequency divider.
LIMITERS
As a technician, you will be confronted with many different types of LIMITING circuits. A
LIMITER is defined as a device which limits some part of a waveform from exceeding a specified value.
Limiting circuits are used primarily for wave shaping and circuit-protection applications.
A limiter is little more than the half-wave rectifier you studied in NEETS, Module 6, Introduction to
Electronic Emission, Tubes, and Power Supplies. By using a diode, a resistor, and sometimes a dc bias
voltage, you can build a limiter that will eliminate the positive or negative alternations of an input
waveform. Such a circuit can also limit a portion of the alternations to a specific voltage level. In this
chapter you will be introduced to five types of limiters: SERIES-POSITIVE, SERIES-NEGATIVE,
PARALLEL-POSITIVE, PARALLEL-NEGATIVE, and DUAL-DIODE LIMITERS. Both series- and
parallel-positive and negative limiters use biasing to obtain certain wave shapes. They will be discussed in
this chapter.
The diode in these circuits is the voltage-limiting component. Its polarity and location, with respect
to ground, are the factors that determine circuit action. In series limiters, the diode is in series with the
output. In parallel limiters, the diode is in parallel with the output.
SERIES LIMITERS
You should remember, from NEETS, Module 7, Introduction to Solid-State Devices and Power
Supplies, that a diode will conduct when the anode voltage is positive with respect to the cathode voltage.
The diode will not conduct when the anode is negative in respect to the cathode. Keeping these two
