Electronic Circuit Design Lab Experiments

To verify the working operation of Crystal Oscillator.

Sep 24 2023

Aim

Apparatus Required:

Breadboard ,Workstation, Function Generator, Trainer Kit, Patch cords, DC Power supply

The instrument comprises of the following built in parts:-

One Fixed Output DC Regualted power suppIy + 12VDC.
Circuit consists of Transistor (SL100), Inductance (50Mh), Resistance & Capacitors combination
One Crystal capacitor (10MHz) is provided on the front panel.
Circuit diagram for crystal oscillator is printed on the front panel and sockets are provided to connect the CRO across output.

Theory:

Many electronic devices require a source of energy at a specific frequency which may range from a few Hz to several MHz. This is achieved by an electronics device called oscillator. Oscillators are extensively used in electronics equipment.For eg. In radio and television receivers oscillators are used to generate high frequency wave (called carrier wave) in the tuning stages. Audio frequency & radio frequency signals are required for the repair of radio, television & other electronics equipment. Oscillators are also widely used in radar, electronics computer& other electronics devices. An electronics devices that generates sinusoidal oscillations of desired frequency is known as a sinusoidal oscillator. The basic components of an oscillator are:-

Tank Circult
Transistor
Feedback Circuit

Oscillator is an important device for many electronics circuit applications and its prime function is to generate wave forms at constant amplitude and desired frequency. Basically an oscillator is an electronics circuit which converts DC supply voltage to an output wave form of some frequency. The oscillator circuit must also be capable of producing sustained oscillations. . The oscillators are classified into two basic categories: Sinusoidal& Non- sinusoidal. If the wave form generated looks like sine wave, the circuit is called a sinusoidal oscillator and the circuit producing all other wave forms are called non- sinusoidal oscillator. Sometimes, the oscillators are also classified on basis of frequency of the generated wave form, viz. Audio frequency, Radio frequency and ultrafrequency oscillators

A Crystal Oscillator is basically a tuned oscillator. It uses a piezoelectric crystal as a resonant circuit.The crystal provides a high degree of frequency stability. Therefore, the crystal oscillators are used whenever great stability is required. Examples are communication transmitters, digital clock etc. Each crystal has a natural frequency f which is given by

f = k/t

Where k is constant and t is the thickness of the crystal. It is clear that frequency is inversely proportional to crystal thickness. The thinner the crystal, the greater is its natural frequency and vice- versa However, extremely thin crystal may break because of variations. This puts a limit to the frequency obtainable. In practice, frequency between 25kHz-10MHz have been obtained with crystals.

Procedure:

Connect the CRO probes across output sockets of the oscillator.
Switch ON the instrument as well as CRO & observe the output .Wave shape on CRO and note down the frequency of oscillation.From CRO or from frequency Counter. The frequency of oscillation will be approximately 10MHz.

Standard Accessories:

Instruction Manual (DOC668).

Optional Accessories

Cathode Ray Oscilloscope (CRO) or Frequency Counter.

Results:Result has been verified by calculating frequency of Oscillator

Viva Questions:

Q.-1. Explain High Frequency Oscillator?

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Q.-2. Derive the expression of frquency for Hartley Oscillator?

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Q.-3. Derive the expression of frequency for Colpitt’s Oscillator?

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