NEETS Module 9 - Introduction to Wave- Generation and Wave-Shaping
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A TRAPEZOIDAL WAVE looks like a sawtooth wave sitting on top of a square wave. The leading edge is called the JUMP voltage.
A TRIGGER is a very narrow pulse used to turn on or off another circuit.
A MULTIVIBRATOR is used to generate a square or rectangular wave. A multivibrator is basically two amplifiers with regenerative feedback.
The ASTABLE MULTIVIBRATOR has no stable state. The transistors alternately switch from cutoff to saturation at a frequency determined by the RC time constants of the coupling circuits.
The MONOSTABLE MULTIVIBRATOR has one stable state. One transistor conducts while the other is cut off. An external trigger must be applied to change this condition.
The BISTABLE MULTIVIBRATOR has two steady states. It remains in one of the stable states until a trigger is applied. It then switches to the other stable state until another trigger is applied.
The bistable multivibrator is also known as a FLIP-FLOP. The two inputs are SET and CLEAR. The two outputs are "1" and "0." A trigger pulse on the set input will cause the "1" output (negative or positive voltage depending on the type transistor used). At the same time the "0" output will equal 0 volts. This is the SET state.
A CLEAR STATE of a flip-flop exists when the "1" output measures low voltage (or 0 volts) and the "0" output is high voltage. The flip-flop will flop to the CLEAR state only upon application of a trigger pulse to the CLEAR (C) input.
There is a third lead on some flip-flops. This lead is the TOGGLE (T) input. Every time a trigger pulse is applied to the (T) input, the flip-flop will change states.
BLOCKING OSCILLATORS are used in applications which require a narrow pulse with sharp leading and trailing edges. They are used as TRIGGER GENERATORS or FREQUENCY DIVIDERS.
A SAWTOOTH GENERATOR voltage waveform has a linear change in voltage and a fast recovery time. The linear change in voltage is generated by taking the output from a capacitor. The sawtooth voltage waveform is used to provide electrostatic deflection in oscilloscopes.
A TRAPEZOIDAL GENERATOR voltage waveform is used to provide, a linear increase in current through a coil. A trapezoidal wave begins with a step or jump voltage, then a sawtooth wave. A trapezoidal wave of voltage is used in electromagnetic deflection display devices.
ANSWERS TO QUESTIONS Q1. THROUGH Q14.
A5. RC coupling networks.
A9. SET state.
A11. Ten percent.
A12. Decreases linearity.
A13. To allow the capacitor time to discharge
A14. A resistor.
NEETS Table of Contents
- Introduction to Matter, Energy,
and Direct Current
- Introduction to Alternating Current and Transformers
- Introduction to Circuit Protection,
Control, and Measurement
- Introduction to Electrical Conductors, Wiring
Techniques, and Schematic Reading
- Introduction to Generators and Motors
- Introduction to Electronic Emission, Tubes,
and Power Supplies
- Introduction to Solid-State Devices and
- Introduction to Amplifiers
- Introduction to Wave-Generation and Wave-Shaping
- Introduction to Wave Propagation, Transmission
Lines, and Antennas
- Microwave Principles
- Modulation Principles
- Introduction to Number Systems and Logic Circuits
- Introduction to Microelectronics
- Principles of Synchros, Servos, and Gyros
- Introduction to Test Equipment
- Radio-Frequency Communications Principles
- Radar Principles
- The Technician's Handbook, Master Glossary
- Test Methods and Practices
- Introduction to Digital Computers
- Magnetic Recording
- Introduction to Fiber Optics