In this note, we are going to know about Function Generator Block Diagram and Working Principle of It. Welcome to Poly Notes Hub, a leading destination for engineering notes for diploma and degree engineering students.
Author Name: Arun Paul.
What is Function Generator?
A function generator is an electrical test device that produces a variety of waveforms, including sine, square, triangle, and sawtooth, over a range of frequencies. It is widely used for developing, testing, and troubleshooting electrical circuits.
Specifications of Function Generator
- The frequency range typically from few Hz to several MHz.
- Sine, square, triangular, sawtooth, and pulse waveforms are generated by this signal generator.
- It has adjustable voltage output, typically from a few millivolts to several volts.
- Output impedance, generally around 50 Ohm.
- AM, FM, or PM modulation techniques are used for advanced function generators.
- It allows frequency variation over a period for testing.
Function Generator Block Diagram and Working
Here is the block diagram of function generator –
- Frequency Control Network: The Frequency Control Network determines the oscillation frequency of the function generator. It comprises of an external frequency control element, usually a variable resistor or capacitor, that regulates the rate at which the integrator charges and discharges. Users can edit this control to change the frequency of the output waveforms. The current sources and capacitor in the integrator circuit are primarily responsible for frequency regulation.
- Upper and Lower Contact Current Sources: The triangle waveform is generated mostly by the Upper and Lower Constant Current Sources. The higher current source delivers a constant current to charge the capacitor in the integrator, resulting in a linear increase in voltage. Similarly, the lower current source generates reverse current, which discharges the capacitor and results in a linear drop in voltage. These current sources keep the waveform stable and symmetrical across time.
- Integrator: The Integrator is a critical component in creating the triangle waveform. It converts the constant current from the higher and lower current sources to a voltage that increases or decreases linearly. Because an integrator accumulates charge over time, the output voltage follows a straight line ramp, resulting in a triangular waveform. The frequency of this waveform is determined by the pace of charging and discharging, which is affected by the frequency control network.
- Voltage Comparator or Multivibrator: The Voltage Comparator (Multivibrator) generates a square wave output from a triangular waveform. It continually compares the integrator’s output voltage to a predetermined reference level. When the integrator voltage hits a specific level, the comparator switches output states, causing the upper and lower current sources to alternate. This quick switching generates a square wave with sharp transitions between high and low states, making it suitable for digital and timing applications.
- Output Amplifier #1: The voltage comparator generates a square wave signal, which the Output Amplifier #1 processes and amplifies. This guarantees that the signal has the proper amplitude and driving capability before it is transmitted to an external circuit or device. The amplifier performs impedance matching and signal conditioning to increase the waveform’s usefulness.
- Resistance Diode Shaping Circuit: The Resistance Diode Shaping Circuit converts the triangle waveform into a sine wave. A triangle wave, unlike a sine wave, has linear rising and falling edges. This circuit uses a network of resistors and diodes to soften the waveform’s edges, gradually changing it into an approximate sine wave. The accuracy of this transition is determined by how the shaping circuit is designed.
- Output Amplifier #2: The Output Amplifier #2 amplifies the sine wave output from the shaping circuit to a useful level. Similar to a square wave amplifier, it ensures that the signal has enough amplitude and stability for external usage. The resulting sine wave output can then be applied to a variety of applications, including signal testing, modulation, and waveform creation.
Working Principle of Function Generator
This is the function generator working principle or describe that how function generator works –
A function generator works by generating and transforming waveforms using an oscillator, an integrator, and waveform-shaping circuitry. It starts with a voltage controlled oscillator (VCO), which sets the fundamental frequency of operation using an externally regulated voltage. This voltage controls the charging and discharging of a capacitor in the integrator circuit, resulting in a linearly increasing and decreasing voltage and a triangle waveform.
Once the triangle waveform is created, it is passed into a voltage comparator, which serves as a Schmitt trigger or multivibrator. When the triangular wave reaches specified threshold levels, the comparator switches states and outputs a square wave. This square wave is then routed through an output amplifier to ensure the proper voltage level and impedance matching for external use.
The triangular waveform is then processed in a resistance-diode shaping circuit to generate sine waves. This circuit smoothes the edges of the triangle wave and converts it into a sine wave. The curved sine wave is then amplified by another output amplifier to get the appropriate signal strength.
The function generator lets users utilize knobs or digital interfaces to adjust parameters including frequency, amplitude, and waveform selection. By altering these parameters, the user can change the behavior of the underlying circuits, resulting in diverse waveform outputs for different applications.
Function Generator Applications
Here are the applications of function generator –
- Used for testing amplifiers, filters, and other circuits.
- Helps in designing and testing RF and modulation circuits.
- Used in laboratories for circuit analysis and demonstrations.
- Generates audio test signals for speakers and microphones.
- Useful for simulating different signals for microcontrollers and processors.