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Wein Bridge Oscillator
The key objective of this project is to design a Wien Bridge oscillator using PSpice software. The Wien bridge oscillator comprises an Op-Amp and a parallel and series RC feedback circuit.
The Wien Bridge is one of the simplest and best known oscillators and is used extensively in circuits for audio applications.
The aim was to understand the use of Pspice and also to design the Wein Bridge Oscillator to simulate the output of the circuit and frequency for a fixed value of R and C.
WAVEFORM PRODUCED FOR 1 Hz to 5Hz FREQUENCY CHANGING THE VALUE OF RESISTORS
PSpice : is one such software that allows users to design and simulate Analogue circuits. It helps the user to design, simulate, test and troubleshoot analogue circuits. It also helps the user to explore changes in the circuit design and thus makes the design process more efficient and faster.
The different frequencies that had to be obtained were supposed to be calculated by varying the values of R and C as . Positive feedback is the key to oscillation process and the only input is a DC input.
Objectives
Design a Wein bridge oscillator using Pspice using an OP-AMP and a parallel and series RC feedback circuit. Simulate the output of the circuit and frequency for a fixed value of R and C. Simulate the output signals for a range of values of R and C to oscillate the output frequency from 1 kHz to 5 kHz.
The Circuit
There are many types of oscillators depending on the type of output waveform it produces. A sinusoidal oscillator is a circuit that produces sine wave output without any external signal excitation. A feedback oscillator consists of two blocks, a frequency selective circuit and an amplifier.
A Wien bridge oscillator comprises an Operational Amplifier (Op-Amp) and a Wien bridge network. The bridge comprises two resistors and two capacitors. The fundamental part of the Wien bridge oscillator is the lead lag circuit (Wien Bridge network). The lead lag circuit is formed by a series RC circuit in series with a parallel RC circuit
In order to get the output waveforms for the range to , the Parametric option available in the Analysis Setup had to be used.
Using the Parametric option, it was made possible to get multiple output waveforms by keeping the capacitance constant ( ) and varying the resistance by incrementing it by a value decided by the user. This change in the resistance brings about a change in the frequency.
The frequency of the oscillator depends on the Resistors and the capacitors from the Wien bridge network. The frequency of the oscillator can be easily altered by connecting a variable resistor in the Wien bridge network. As a result it can generate a large range of frequencies.
The output is relatively free from distortion and its frequency can be varied easily.The oscillator is simple in design, compact in size, and remarkably stable in its frequency output.
The maximum frequency output is limited because of amplitude and the phase-shift characteristics of amplifier.It can be inferred that for constant values of either parameter and the other varying (resistance or capacitance), we obtain equal frequency values for the range tested (1Khz to 5Khz).