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  1. LvW

    New idea for oscillator

    Bob - do you think, such a device will oscillate? I am afraid it will lock.
  2. LvW

    New idea for oscillator

    Here is one of the general definitions: Oscillators are systems producing timing information without any external information. An example of a simple mechanical oscillator is the pendulum clock
  3. LvW

    Differential Amplifier

    I think, you have no other chance than to assume for both transistors a biasing DC voltage between base and emitter of Vbe=(0.65...0.7) volts. The exact voltage is not known and is not too important because of of the negative feedback effect of Re. Starting with such an assumption it shouldn`t...
  4. LvW

    Gain decrease in the in-band of a common emitter amplifier.

    To be honest - I am surprised that the difference is not larger than 1.5 dB. At frequencies as large as 100 Mhz you have to consider many parasitic effects that are not included in the simulation setup.
  5. LvW

    Simple maths resistance exercice

    If you have any specific question - don`t hesitate. Up to now - I see no question.
  6. LvW

    Basic understanding of low pass filter

    messy - I suppose you know the trem "voltage divider". Now - imagine such a divider consisting of a resistor R and a capacitor C.. The frequency-dependent impedance of the capacitor is Zc=1/jwC. With a sinusoidal voltage Vin across both parts, the voltage across the capacitor is...
    • LvW
    • Post #15
    • Forum: Audio
  7. LvW

    Basic understanding of low pass filter

    messy - with reference to your last sentence: I must admit that I do not understand everything what you have written - nevertheless, I am afraid you are not on the right track. Again, you are back in the time domain (charging, half cycle,...). This does not help at all to understand what a...
    • LvW
    • Post #12
    • Forum: Audio
  8. LvW

    Basic understanding of low pass filter

    messy - during all your readings and investigations you must realize the difference between two basic "domains": "Time domain" and "frequency domain". Otherwise, you cannot understand what`s going on.... (1) In the time domain you describe voltage and current properties of a circuit as a...
  9. LvW

    Inverting op amp feedback parameter B

    Yes - it is common practice to apply the general feedback model as shown in your post#6. Here, the input signal Vn that arrives directly at the inverting (minus) input node of the active device (opamp) , consists of two parts (superposition): Vn=Vn1+Vn2. One part is derived from the output...
  10. LvW

    Inverting op amp feedback parameter B

    Yes - and these explanations can also be found in each relevant text book. Therefore, my recommendation: Before asking similar questions consult a serious textbook and do not blindly rely upon any internet-sources.
  11. LvW

    Inverting op amp feedback parameter B

    Harald - I have some problems with your contribution. * β = R1/R2 is NOT correct. * β = (R1+R2)/R2 can also not be correct because a passive feedback factor can never be >1. Ignacio: The expression for the feedback factor on page 10 is wrong! In both cases - inverting and non-inverting...
  12. LvW

    Hi, can somebody help me with feedback circuit

    Regarding DC bias: The circuit has no biasing voltages at all. And - as mentioned - the emitter resistor provides negative DC feedback (and - yes- contributes to bias) and R3-L2 provide negative ac feedback!! What is the purpose of R1-L1-C1 feedback path? Does it always work as a feedback loop...
  13. LvW

    Hi, can somebody help me with feedback circuit

    Michael...so you now really understand the meaning, the task and the characteristics of the two feedback loops in the circuit? (I hope you know that R3-L2 also provides feedback). I would be surprised...
  14. LvW

    Transistors amplification

    Bob - what I mean is the following: The phrase "a transistor ....controls a large current based on a small current" implies that the BJT would be a current-controlled device, right? In contrast, the contribution from hevans (..."you should reconsider your "knowing" that a transistor amplifies...
  15. LvW

    Transistors amplification

    Bob - this statement contradicts the contribution from hevans1944. In order not to confuse the questioner - perhaps you reconsider the above quoted sentence?
  16. LvW

    Sallen and Key Nodal Equations

    Everything OK with Harald`s answer. Nevertheless, according to my experience it is more easy to use Kirchhoff`s current law for each oif the various nodes (using the voltages between each node and ground).
  17. LvW

    Finding a high frequency differential amplifier Transfer Function

    For ac analyses, the current source may be replaced by an open circuit - that`s correct. However, if you want to analyze bias conditions...what do you think: Is the DC current source important or not?
  18. LvW

    Operational Amplifier Internal Resistance

    To me, it is not clear what your question is: * "Internal resistance"? What is that? Definition? * "Input resistance of operational amplofier"? At the inverting input? Or are you asking for the input resistance of the whole circuit?? * Why do you think that R4 and R5 play a major role??
  19. LvW

    Finding a high frequency differential amplifier Transfer Function

    Why do you ignore the current source at the common emitter node of Q1 and Q2. Yes - in this case, the "second transistor is not-functional".
  20. LvW

    Question about active low pass filtering

    There are three points to be answered: * Is there any negative DC feedback (stable bias point)? * What about the gain for low frequencies? * What about the gain for rising (that means: high) freqiencies?
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