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  1. LvW

    Designing an Active Band Pass Filter

    Sorry, I wrote that the ratio of the two resistors in your circuit should be 4Q²=400 in case of Q=10. That was an example only. Therefore, select two resistors having this ratio and calculate the corresponding capacitor value (for two equal capacitors) according to the formula for the center...
  2. LvW

    Designing an Active Band Pass Filter

    I have some experients with filters. For a Q value of 10 and two equal capacitors you need a resistor ratio of 4Q²=400. In this case, the 3dB-bandwidth is B=fo/Q. It is up to you to decide which bandwidth meets your requirements. EDIT: "Just out of interest, what would generally be considered a...
  3. LvW

    Designing an Active Band Pass Filter

    I did not check your dimensioning in detail - however, I think the resistor spread must be much larger (larger resistor ratio) for two equal capacitors. In the mentioned Paper the example is for Q=0.707. That means: bandwidth B=1.4*Fo. This is a "bandpass" that does not deserve this name. For...
  4. LvW

    Designing an Active Band Pass Filter

    As I have explained in my former answer - it is a second-order filter (one complex pole pair). However, the transition from the passband to stopband has single-oder properties only (slope 20dB/dec). For this reason, some authors consider such a bandpass filter to be "first-order" only. However...
  5. LvW

    Designing an Active Band Pass Filter

    The answer depends on your damping requirements oiutside the pathband. A lowpass-highpass combination is appropriate if the bandwidth is rather large and if - at the same time - you need a slope of at least 40dB/dec for the transition from the passband to stop band. A second.order bandpass...
  6. LvW

    Help with MFB second order high pass filter

    Chris - your circuit is wrong. It has no dc feebdack, which is necessary for each opamp. The 17.9k resistor must be connected directly to the inv. input.
  7. LvW

    Oscillator test

    What about a test receiver? (Any oscillator works as a transmitter).
  8. LvW

    Oscillator test

    Do you have the chance to measure the current vs. time (oscilloscope) going into the circuit?
  9. LvW

    gain amplifier

    Yes - my first tip: Show us the circuit. If a circuit does not work - nobody can find the reason without knowing how it looks like.
  10. LvW

    Why does the current always remain the same in a series circuit?

    For my opinion, it is the other way round: We speak about a series connection of several parts if - driven by corresponding voltage source - there is the same current through these parts.
  11. LvW

    Why does the current always remain the same in a series circuit?

    Life24 - are you speaking of two different circuits or of a series connection of two resistors?
  12. LvW

    Parameters needed to design a Butterworth filter?

    Both parameters (passband ripple and stop attenuation) must be specified by YOU! These parameters are determined by the specific application - sometimes passband ripple is allowed and sometimes not. Some applications specify the stopband with 20 dB attenuation (minimum) and some others require...
  13. LvW

    How to get Cs and Rs?

    OK - what I see is the following (although I cannot find Rs and Cs in your circuit): * You have a passive lowpass with a cut-off frequency of app. 4 MHz. * Your input signal is squarewave with a frequency of app. 4 kHz. * It is, therefore, no surprise that no real filtering takes place - and the...
  14. LvW

    How to get Cs and Rs?

    Any idea? About what? At first, YOU have to answer some questions in order to let us know what you want. 1.) What are the purposes and the requirements of the circuit? 2.) What was the input signal for the LTSpice simulation? 3.) Input signal for oscilloscope measurements? Note: Helpful...
  15. LvW

    Transistors / hfe / Active region conflicts

    Yes - most probably, you are right. Therefore: I would be very happy if you could teach me how a transformer-coupled amplifier can work along a DC load line. I am curious for your anwer. Do you still rely on the shown graph? Surprising situation.
  16. LvW

    Transistors / hfe / Active region conflicts

    Laplace - do you uncritical believe everything you find in the net? I can tell you that the drawing you have posted is completely nonsense (by the way: the whole site "electronic-tutorials" contains many errors). 1.) Do you recognize that the "input signal" is across the Vce axis? And the...
  17. LvW

    Transistors / hfe / Active region conflicts

    Simply false. Do you know how the output of a large-signal push-pull stage looks like (class-B operation)? It is a clean copy of the Ic=f(Vbe) characteristics - including the "dead zone" (cross-over distortions). More than that - the characteristic curves in Fig. 1 show a mathematical relation...
  18. LvW

    Transistors / hfe / Active region conflicts

    ...emitter feedback for Ib... Sorry - it`s pure nonsense. Don`t you have any access to a textbook which explains to you how "emitter degeneration" works? In short: Ic increase (due to temperature or tolerance effects) increases the dc voltage Ve across Re. That means: For a fixed voltage at the...
  19. LvW

    Transistors / hfe / Active region conflicts

    The base current Ib is "controlled by the collector current" ? In post#61 you wrote exactly the opposite: It's probably just too simple to understand. Ib controls Vbe, Vbe controls Ic. Are you able to realize the contradiction? This prooves that you have a certain lack of understanding for the...
  20. LvW

    Transistors / hfe / Active region conflicts

    `...emitter feedback for Ib? It is slowly becoming funny. As you do not want to "repeat that explanation again" I kindly ask you to tell me where you have already explained such a surprising BJT property. By the way: Have you ever heard that RE provides VOLTAGE feedback which works only in case...
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