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  1. LvW

    eMOSFET and common emitter amplifier

    Hevans1944, I completely agree to everything you wrote. However, just a small comment: Because you have mentioned the limitations and the necessary approximations of the simulation program I think we should realize that all hand made calculations (based on formulas) will contain much more...
  2. LvW

    eMOSFET and common emitter amplifier

    Hevans1944 - may I ask you: Why do you hate to say this? For my opinion, circuit simulation programs are a very helpful and versatile tool for improving the understanding of electronic circuits - provided the user is familiar with the properties and limitations of the various available analyses...
  3. LvW

    eMOSFET and common emitter amplifier

    Are you familiar with the properties and consequences of negative feedback? In both circuits the resistor in the source resp. emitter path provides negative feedback. More than that, it would me much easier for us to help you if you would spend some time for typing your questions instead of...
  4. LvW

    Waveform simulation in LTspice

    Of course, you must tune the parts values according to your timing requirements (T1 and T2).
  5. LvW

    Waveform simulation in LTspice

    Ratan - didn`t you read my answer? A simple RC-CR bandpass will do the job to transfer a step signal into the desired waveform . The example provided with my anser is a RC lowpass (1k, 16nF) in series with a CR highpass (16n, 100k).
  6. LvW

    Waveform simulation in LTspice

    The requested transient waveform is a typical step response of a low-Q second-order bandpass. So - it shouldn`t be a problem to create such a signal.
  7. LvW

    cant find the tranfer function of 2nd order lpf

    Of course, I mean that the VALUE of this resistor is not very important - and it can be replaced by a simple short. Otherwise, we wouldn`t have a unity-gain amplifier.
  8. LvW

    cant find the tranfer function of 2nd order lpf

    This resistor is not very imporetant - and it does not influence the transfer function. The only purpose is as follows: There is always a small dc bias current into the opamp inputs. At the non-inv. input this current produces a small dc voltage which may cause a small dc offset at the output...
  9. LvW

    cant find the tranfer function of 2nd order lpf

    Your circuit is one of the classical 2nd order structures: Unity-gain Sallen-Key lowpass. Google for it - and you will find many, many answers.
  10. LvW

    oscillator help

    Here is another "interesting" conclusion from Colin at the end of his explanation how a phase shift oscillator works: Quote: "The circuit works completely differently to anything described in any Text Book. The transistor operates on a rising and falling CURRENT (increasing and decreasing...
  11. LvW

    Merry Christmas and a happy new year ...

    Harald - thank you. And the same to you and your family.
  12. LvW

    oscillator help

    see here: http://www.talkingelectronics.com/te_interactive_index.html Then click: Left columne: "Transistor Amplifier" and "Biasing a Transistor" (Text right to the 5. Figure).
  13. LvW

    oscillator help

    Just to complete my previous comment: Excerpt from "talking Electronics": Suppose the transistor gets warm on a hot day and looses gain. The collector voltage will rise and the current through the load resistor will decrease. The current through Re will also decrease and the voltage across it...
  14. LvW

    oscillator help

    Colin, I must admit that - up to now - I did not read all of your contributions in"talking electronics". However, I only can hope that none of the thousands of vistors of your webside was trying to follow your "explanations" about BJT basics (in particular base biasing and function of the...
  15. LvW

    oscillator help

    Yes - me too. More than that, I always switch on power supply at t=0.
  16. LvW

    oscillator help

    CDRIVE - I can agree to all of your remarks with one tiny exception: If properly arranged SPICE simulators will have no problems with linear (sinusoida) oscillators. However, one must know how to command the simulator. My experience: In nearly ALL cases, it is the user who makes errors - not...
  17. LvW

    oscillator help

    I think, it is not appropriate for this circuit to think in "ON" and "OFF" terms. The circuit produces a sinusoidal output!
  18. LvW

    oscillator help

    Is this a contradiction? Of course, there is a cap in parallel to the inductor. As a consequence, we have a tuned circuit, which determines the oscillator frequency. And a part of the voltage across the tank is fed back to the emitter. The transistor operates as a common-base amplifier - and...
  19. LvW

    Designing an Active Band Pass Filter

    At first, you should not mix different filter topologies (like Sallen-Key, multiple feedback,...) with the various approximations available to shape the filter functions. However, such a shaping requires more than one single pole pair - that means: It is not applicable to first-order...
  20. LvW

    Designing an Active Band Pass Filter

    A second-order bandpass is a bandpass of lowest order possible (to be compared with a first-order lowpass). For such circuits we cannot discriminate between various approximations like Butterworth, Chebyshev,... There is only one single frequency response.
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