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  1. LvW

    Opamp Power Supply

    Harald, perhaps the following applies only to me - however: To me, this sounds as if a so called "rail-to-rail opamp" would be an alternative solution to single-supply operation. I am sure, that´s not what you wanted to express, correct?
  2. LvW

    Opamp Power Supply

    In short: Each opamp needs a voltage between the power pins in order to work properly - that means: To be able to amplify in its linear transfer characteristics. 1.) Then, the best quiescent operating point (DC output voltage) is in the middle of this region. Then, we have equal room (above and...
  3. LvW

    biasing this op amp

    You have mentioned to use split supply. In this case, you do NOT need a virtual ground node. Instead, use the pos. supply voltage between the corresponding opamp pin and ground - and do the same with the negative supply voltage. In this case, the ouput voltages of the opamps will be centered at...
  4. LvW

    biasing this op amp

    You have forgotten any common ground reference!
  5. LvW

    How can I build a sine wave generator with variable phase?

    Fish - I fully agree with you. My answer concerns only the point of "changing the phase of an oscillatory signal" - nothing else. If such an approach can be a starting point for any noise cancellation system is outside of my region of experience.
  6. LvW

    How can I build a sine wave generator with variable phase?

    All you need to do is slowly tune up and down the frequency of your signal generator. This will change the phase - if compared with any external signal. However - this is, more or less, a trial-and-error procedure because the amount of phase changed is unknown.
  7. LvW

    Resonance Frequency

    OK - problem solved because C*Rc²=1E-9*1E6=1E-3 > 1E-6.
  8. LvW

    Resonance Frequency

    Hi Ratch, I didn`t check your calculation - and I was too lazy for calculating by myself. However, apparently there is a conflict beween your result (C*Rc²>1) and my simulation. As I have mentioned above, according to simulation (symbolic analyzer as well as PSpice) the imaginary part of the...
  9. LvW

    Resonance Frequency

    Perhaps it is interesting to numerically compare the various alternatives (definitions): Example circuit: Rc||C=1kohm||1nF Rs=250 Ohms; L=10uH. Results (Simulation): |Imax| at 1.76 MHz IMG(I)=0 at 1.583 MHz |Vout,max| at 2.78 MHz.
  10. LvW

    Resonance Frequency

    MikaM - what is your conclusion? Which definition will you use - and why?
  11. LvW

    Resonance Frequency

    Yes, that is another possible - perhaps the best(?) - criterion for defining resonance. It is intersting to note (prooved by simulation) that the peak of the total current through the network is NOT identical with the frequency where the current phase is zero (no reactive component).
  12. LvW

    Resonance Frequency

    It`s not as simple. As an example, the resonant frequency of a lossy L in parallel to a capacitor C is (see, for example, wikipedia):
  13. LvW

    Resonance Frequency

    Yes - but how do you define it?
  14. LvW

    Resonance Frequency

    As I have mentioned - it depends on the definition (max. current or max. output voltage). The current (magnitude) through the whole circuit has a maximum at a certain the frequency f1, but this does NOT mean that the magnitude of the voltage drop across Rs+L has a maximum at the same frequency...
  15. LvW

    LC Oscillator

    So you have tried different concepts which didn`t work satisfactorily (for "some reason") - and you ask us for alternatives. Obviously, it is not easy to answer without knowing what you have done already.
  16. LvW

    Resonance Frequency

    I don`t think that this is true for the shown circuit. The (different) peaks of the current and output voltage depend on the R values. Therefore my question how the resonance point is defined for this circuit.
  17. LvW

    Resonance Frequency

    How do you define "resonance" for this circuit? The point (frequency) of maximum current is not identical with the point of max. output voltage.
  18. LvW

    Finding rate of change of capacitor discharge?

    Yes - each R-C lowpass charges UP to 63.2% of the final value within a time t=T=RC. However, you were asking for a discharging process! It is even possible (without calculating) to make a good estimate of the result.
  19. LvW

    Finding rate of change of capacitor discharge?

    Ask yourself what the output - according to the following equation - will be for a discharging time t approaching infinite. Is the result OK? Vc / V = 1 - e^(-t/T)
  20. LvW

    Finding rate of change of capacitor discharge?

    Why do you think that you can use the same equation as for the charging process?
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