An electronic instrument that generates repeating and non-repeating voltage waveforms is a Signal generator. Generally an ideal signal generator is molded as a voltage source. Signal generator can also be called as functional generators, microwave generator, pitch generator, RF, arbitrary waveform generator. This electronic device generates an electronic signal which can be either analog or digital. Signal generator will delivers an accurate calibrated signal at frequencies from audio to the microwave range. This is used mainly in the developing and testing of electronic hardware. These signals can be adjusted according to frequency, designing, testing, repairing, troubleshooting, modulation, output, waveform and impedance.
Why to Use Signal Wave Generators ?
Signal wave generators are used in the following cases
- To test and characterize the electronic device and circuit.
- The signals generated are usually periodic.
- Information carriers for communication system.
- Control systems and time clock for computers.
There are two approaches for generating signals
- Linear oscillator is an amplifier and also a frequency selective positive feedback network.
- Non-linear oscillators used for multivibrators.
For example, some of the signal generators are sine generator, frequency generator, function generator and pulse generator.
Sinusoidal Wave Generator
The wave form that can be easily generated is a sine wave. Here is the circuit gives below which will generate the sine wave. This circuit will first generate square wave and later generates a sine wave at the required frequency. The amplifier A1 which is configured as an astable oscillator with the frequency determined by R1 and C1. In this circuit two pole low pass filter, using A2 filter the output will be from the A1 which is a square wave.
The filter used is a unity gain Sallen-Keys filter its cutoff frequency is equal to square wave frequency from A1. From the fundamental frequency and off harmonics of the fundamental frequency square wave is made up. Here most of the harmonic frequencies and fundamental frequency is being filtered mostly and output remains at A2. The fundamental components of a square wave will approximately 1.27 times the peak amplitude of the square wave. The amplitude of the sine wave output will be about 87 percent of the peak of the square wave. The peak of the square wave will rely on the output swing specification of the amplifier and the amplifier supply voltage. Along with this peak of the sine and square wave will track changes in the amplifier’s supply voltage.
The specified frequency along with the value of capacitor C1 and based on these values R1, C2, C3, R4 & R5 are calculated. The specific values of R2, R3, and R4 are 1K Ohms these values should match in the values to help minimize error in the actual frequency of operation compared to the calculated frequency of operation. The value of C1 is 0.001µf.
Applications of sine wave generator mainly involves in the following
- House appliances
- AC motors
Functional Wave Generator
A functional generator is used to generate different types of electrical waveforms over the wide range of frequencies which uses electronic test equipment or a software. The waveforms which can be easily generated are sine waveform, square waveform, triangle wave form and saw tooth wave form. Functional generator covers both audio frequency and RF frequency. Function Generator controls frequency, DC offset, Duty cycle.
There are three different types of functional generator
- Analogue function generator
- Digital functional generator
- Sweep function generator
Analogue Function Generator
This is the first type of signal generator before the existence of the Digital functional generator. Some of its advantages over digital are cost effective, simple to use and maximum frequencies.
Digital Function Generator
One among the many ways of generating the digital waveforms most preferable will be direct digital synthesis (DSS). The fundamental ideas of DSS technology are generating an arbitrary periodic waveform from a period ramp signal and generating a digital ramp.
Direct digital synthesis uses a phase accumulator, a DAC and a look up table which contains waveforms. It offers high stability and accuracy
Sweep Function Generator
It will sweep its frequency by digital technology and also by analogue. Sweep function is able to sweep up to 100:1. The sweep can be featured in linear and logarithmic
Here we can observe that functional generator is giving multiple outputs square, triangle and sine.
Generation of Triangle Wave
Triangle wave is one among the generations of the function wave generator. Triangle wave can be generated with a simple circuit with is an oscillator.
The later part of the circuit, i.e., second half is an inverting Integrator. Initially the first operational amplifier starts with its two inputs which are unknown. Here, let’s assume operation starts with positive sign which is slightly higher than negative i.e., ground. The operational amplifier’s positive power supply voltage, its max o/p is 15V in this circuit. By this positive i/p, the Integrator’s o/p falls to a constant.
Resistance 10k & 4k acts as voltage divider which put the first operational amplifier’s positive i/p 4/14th of the way from the 2nd operational output to the 1st operational o/p. Once this o/p reaches the ground, the 1st o/p switches polarity, and the Integrator direction, forming the other half of the triangle. When the 1st polarity gains, a new cycle begins.
Functional generator controls Frequency, Waveform Types, Sine, Square, Triangle, DC Offset, and Duty Cycle
Applications of functional wave generator mainly involves in the following
- In the development and research
- Electrical and electronic equipment repair business
- In the Electronic hobbyists
- It is used in the many educational institutions
- Response or stimulus testing, frequency response characterization
- In the circuit signal injection.
Pulse Wave Generator
A pulse generator allows control of the pulse which are repetition, pulse width, pulse amplitude and pulse width. It is an electronic circuit used to generate the rectangular pulse.
Pulse generator may use digital or analogue or even both in some cases to generate the output. It controls the rise and fall of the pulses which can be determined by frequency or period adjustment.
The basic pulse generator
Pulse Width: To generate different kinds of waveforms, the pulse width can be varied.
Repetition Rate: It plays a key role when it is in the mode of ‘free run’.
Pulse Trigger: This can occur in either negative or positive
Pulse Delay: This is adjustable delay when the pulse is triggered in the normal mode.
Pulse Amplitude: This normally used to drive logic circuits. Its amplitude is normally adjustable.
Basic Diagram of Pulse Wave Generator
This circuit stores energy either in an electrostatic field or in a magnetic field, and the immediate discharge of a fraction or all of this stored energy into the load.
This pulse generator with duty cycle made with 555 timer IC. The circuit shown below is an astable multivibrator with a 50% duty cycle. It is different from the standard design of a 555 is, the resistance between pins 6 and 7 of IC composed of R2, D1, D2, P1 and P2.
The two diodes D1 and D2 is set for a definite charging time for C1 which produces a 50% duty in a normal case. Duty cycle is dependent on P1 and P2
N = 1 + P2/p1
Let suppose p2 = 0 (n = 100%)
Frequency can be approx calculated by
F = 0.69/((2-p1 + p2 + 4.7kΩ)*C1
The Pulse Width and Period will satisfy either of these conditions
Period*(pulse width)/100 = 0
Period*(pulse width)/100 = period
Applications of pulse wave generator mainly involves in the following.
- It is used in the clock signal
- To confirm the proper operation of the device
- They are used in driving switches, optical components and lasers.
- In resistive loads, modulators and intensifiers
- It is used in the testing of the logic circuits
Therefore, this is all about different types of waveform generators with applications which includes signal, sine wave, pulse and function generators. We believe that you have got a better understanding of this concept. Furthermore, any queries regarding this concept or electrical and electronics projects, please give your feedback by commenting in the comment section below. Here is a question for you, what is the main function of signal generator?
- Block Diagram of Functional Generator circuitstoday
- Pulse Generator electroschematics
- Pulse width Waveform sdsu