oscillator


Posted on Feb 5, 2014

An oscillator is a circuit that can generate a frequency source such as a sine wave, square wave or pulse train. An oscillator is fundamentally a combination of a frequency-sensitive circuit such as an LC circuit or a crystal and a negative resistance usually obtained by using an amplifier with positive feedback. Phase shift is the displacement of


oscillator
Click here to download the full size of the above Circuit.

a waveform in time. For example, if a waveform is displaced by a complete wavelength. it is described as having a phase-shift of 360 °. If it is displaced by half a wavelength (i. e. 180 °) one wave will peak where the other is in a trough state and complete cancellation will result. If they are at any other angle of phase-shift, partial cancellation will result. A phase shift oscillator is a simple sine wave electronic oscillator. It contains an inverting amplifier, and a feedback filter which `shifts` the phase by 180 degrees at the oscillation frequency. The most common way of achieving this kind of filter is using 3 cascaded resistor-capacitor filters, at the oscillation frequency each filter produces a phase shift of 60 degrees and the whole filter circuit produces a phase shift of 180 degrees. Thus the total phase shift produced by the three RC networks is 180 °. Therefore at the specific frequency fo the total phase shift from the base of the transistor around the circuit and back to the base is 360 ° The mathematics for calculating the oscillation frequency and oscillation criteria for this circuit are surprisingly complex, due to each R-C stage loading the previous ones. The calculations are greatly simplified by setting all the resistors (except the -ve feedback resistor) and all the capacitors to the same values. In the diagram, if R1 = R2 = R3 = R, and C1 = C2 = C3 = C, then: The Hartley oscillator was invented...




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Frequency Peak Detecting Probe
    RF Recieving Amplifier for 40MHZ
    RF power and VSWR meter
    Magnetic Field Meter
    Furnace Fuel Miser Circuit
    Sensors and Sensing
    12v to 220v converter circuit
    Lead acid battery charger
    High Power Square Wave Generator (0-500V 25A)
    interfacing lcd atmega32 microcontroller atmel studio
    500 metre radio data link



    Top