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  1. LvW

    Phase Shift Oscillator

    Ratch - I think, I can clarify the point. Laplace did multiply his phase (in blue) response of a single RC sections with a factor of "3" - assuming that all three RC sections would be decoupled.
  2. LvW

    Phase Shift Oscillator

    Yes - that´s right. Parasitic phase shift of the opamp(s) is another aspect to be considered. Also this effect speaks against the oscillator topology under discussion because we need a gain of "29". Other oscillator structures work with opamp gains of "3" or even lower - with reduced phase errors.
  3. LvW

    Phase Shift Oscillator

    Yes - the loading of the last RC sections caused by the inverting opamp is one of the disadvantages of this circuit. Of course, one could add a buffer amplifier for decoupling - nevertheless, we still have the problem that frequency tuning of the circuit is rather complicated. These aspects have...
  4. LvW

    Phase Shift Oscillator

    It was not my primary goal to find a circuit which corresponds to the "book formula". (Although I gave him a suitable circuit using an integrator stage, see my post#8). The questioner has shown us a circuit and he gave a formula which does NOT correspond to the circuit. Hence, in post#2 and...
  5. LvW

    Phase Shift Oscillator

    Yes - we need the transfer function of the complete 3rd-order RC network and, then, set the imaginary part of the denominator equal to zero. Then, we solve for w.
  6. LvW

    Phase Shift Oscillator

    In the attachement you have shown that the phase shift for one single unloaded RC section is 60 deg at a frequency of w=1.732/RC. Based on this, how can we derive the formula for a series connection of three coupled RC sections (as presented by Ratch) ? (Comment: Obviously, we cannot assume...
  7. LvW

    Phase Shift Oscillator

    See my last post (EDIT).
  8. LvW

    Phase Shift Oscillator

    Exalibur - your formula applies to another phase shift oscillator (1.732=SQRT(3). More than that - please note that two basic versions of the phase shift oscillator exist: 1.) Three RC lowpass sections: wo=SQRT(6)/RC 2.) Three CR highpass sections: wo=1/[SQRT(6)*RC] More than that, you should...
  9. LvW

    Transistors

    Is this (to "wiggle") not dependent on amplitude and frequency? I think, in case of a low-frequency signal with a sufficient amplitude, the current during a part of the period can be nearly regarded as a rising dc signal? Adam, thank you for replying. And special thanks for the last paragraph...
  10. LvW

    AC Analysis common emitter configuration

    @studentLab: 1.) The gain of a circuit is a small-signal value (dynamic, differential) - hence, you must NOT use the ratio of DC values. 2.) The expression Av=Rc/Re is a rough estimate only. The correct formula is Av=Rc/(re+Re) with re=1/gm=Vt/Ic, As you can see the rough approximation is...
  11. LvW

    Transistors

    OK - no problem. It was my intention only to start/enable in this forum a discussion about a more generalized definition of the quantity we call "current". It seems, however, nobody is interested. (Let me add: I am sure such a generalization is possible). I wonder how a current clamp would react...
  12. LvW

    Transistors

    So - what is the thing we call "displacement current"?
  13. LvW

    Transistors

    I am aware that a conductive wire and a capacitor exhibit major differences in the way they work. That is not my point. Let´s speak about the phenomenon we call "current" only. And I am also aware that "the process cannot go on indefinitely". Let´s concentrate on the main point (DC switch-on...
  14. LvW

    AC Analysis common emitter configuration

    Comparing in post#1 the circuit diagram with the formulas I think that the meaning of "//" is clear: parallel connection.
  15. LvW

    Oscillator circuit - possibly Wien Bridge Oscillator?

    The circuit as shown is very far from being a harmonic oscillator. More than that, the components R7, R6, C2, R8 do not contribute to the desired dynamic behaviour because they act as a load only (with a poor high pass characteristic). Why don´t you try to use one of the well-known circuits...
  16. LvW

    Oscillator circuit - possibly Wien Bridge Oscillator?

    @TFahey OK - you need an oscillator tunable between 5.25 and 5.9 kHz with an amplitude of 1Vpp. Several circuit topologies are possible and extensively described in the literature. The circuit you have shown looks a bit "uncommon" (In fact: I have never seen it and I doubt if it will...
  17. LvW

    Help With an Equation

    I am afraid, there is no help possible without some additional information. *What kind of inverter (opamp or transistor)? *What is RL and Rds ? *What kind of "equation"? Gain?
  18. LvW

    AC Analysis common emitter configuration

    I see two small errors: * First expression: Denominator (re+R4) * Second expression: Numerator R8||R11 (instead of R8||R9).
  19. LvW

    Transistors

    Ratch - certainly, you can describe all the effects connected with charge, voltage, energy,etc. much better than I can. Please, take into consideration that I am using a language that is not my mothers tongue. For my opinion, I didn´t say that "charges go through a dielectric". Please, read...
  20. LvW

    Transistors

    Again, I like to comment to this with a somewhat provokative sentence: A current also exists between the capacitor plates. Let me explain my view (perhaps I am wrong): * What is the thing called "current"? Answer: Movement of charges due to a kind of charge imbalance (called voltage). * The...
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