Sin function generator

Discussion in 'Homework Help' started by tomson, Feb 17, 2011.

  1. tomson

    Thread Starter New Member

    Sep 6, 2010
    16
    0
    I was given the following task : 'Implement sine function generator using four different methods: absolute values, table of differences, polynomial approximation and circuit being on stability limit . Parameters of the generators are Amplitude u=255 V, frequency f=50Hz' . The first three ways are already working but now I have problem with 'circuit being on stability limit'. Where to start with here ? I can simulate the whole circuit with PSIM and programm any logics controller with C++.
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,178
    1,799
    Oscillators are examples of circuits operating at the stability limit. A simple harmonic oscillator is easy to build with a pair of op-amps. There are also the Hartley, Colpitts, and Pierce oscillators that can be used with reactive components to provide the appropriate feedback.
     
  3. tomson

    Thread Starter New Member

    Sep 6, 2010
    16
    0
    I've tried building the hartley generator, but I didn't received anything similar to sinusoidal oscillations

    [​IMG]
     
  4. tomson

    Thread Starter New Member

    Sep 6, 2010
    16
    0
    my fault it works properly when I've disconnected the whole circuit and connected it once again. But now the question is how to set the frequency to 50Hz and amplitude to 255v ? I can control f with inductances (when set to 0.1) but what about amplitude ?
     
    Last edited: Feb 19, 2011
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    That's a lot of voltage for a transistor. A FET or a triode tube might do better.
     
  6. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    The circuit you have posted does not appear to contain any power supply or bias components. It is not clear how it can work: possibly the result you are seeing is simply an undamped transient resonance. In simulations, inductors and capacitors can have unrealistically low losses or even zero loss. This can lead to transient oscillations persisting for longer than would be possible in practice.

    The amplitude of the output from most oscillators is limited by non-linear processes, often in the amplifying device. Typically, the amplitude given by a simple oscillator will be roughly proportional to the supply voltage, and the output level can therefore be adjusted by varying the DC supply.
     
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