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  1. LvW

    Physics of n-p Junction in a diode

    Yes - You are right, the question was not clear. It is clear that the barrier voltage is controlling the diffusion - however, one could ask what is the physical effect that controls the barrier voltage? The electric field in this region? And does this field depend on the space charge or the...
  2. LvW

    Physics of n-p Junction in a diode

    Ratch - your answer gives rise to the question: When the applied voltage changes, then reacts initially the width of the space charge region or the voltage barrier? Remember: Voltage (potential difference) is the integral over the electric field E - and E is the integral over the space charge.
  3. LvW

    driving analog frequency through a digital component

    An interesting exception is the CMOS inverter which allows analog (linear) amplification. The reason is: If biased at Vcc/2 the output is at app. Vcc/2. For this purpose, a (high-valued) resistor beween output and input is sufficient. This property allows to use the quasi-linear part of the...
  4. LvW

    mos operation regions

    I think, there are no "digital parts". Rather we have parts which mostly are operated between two extreme conditions ("digital") or any where in between. That means: We shouldn´t only distinguish between "on" and "off". A ggod example is the CMOS inverter which can be (and is in some...
  5. LvW

    Physics of n-p Junction in a diode

    As a starting point you must try to understand what a depletion regon is - and how it originates (diffusion process and corresponding voltage).
  6. LvW

    Op Amp Stability

    I have seen a lot of textbooks on opamps - but I didn`t get the feeling that a single supply buffer configuration can be "seen in most text books". In many cases, no supply rails are shown at all (because split supply is assumed without mentioning). In many cases, for single supply operation a...
  7. LvW

    Op Amp Stability

    Good morning Adam, I just a short look on the revised post#1 (buffer chapter) and I have the following question: Why did you choose single supply operation? In this case the circuit can work correctly for positive input voltages only. Even an input step of 1V is not allowed. For my opinion...
  8. LvW

    Looking for a good simulator

    TOPSpice is from PENZAR.com
  9. LvW

    Looking for a good simulator

    According to my experience, there is no big difference between the various simulator programs - as far as their capabilities are concerned. Of course, there are differences regarding price and the way how to work with the program (schematic entry, libraries, simulation commands,...). Mostly, I...
  10. LvW

    Solution to this op amp circuit

    I am sure one could discuss about this - but this wouldn´t make much sense in the context of this thread. As you have said before: It is a "matter of opinion, and we all have our opinion."
  11. LvW

    Solution to this op amp circuit

    Since Blacks formula for a system with feedback has proven to be correct (many decades ago), I see no reason not to "have any confidence". Hi Laplace - please, can you justify your criticism? Can you explain why this way to solve the task is not trustworthy? It is just an application of the...
  12. LvW

    Solution to this op amp circuit

    Dan, like always - there are some different ways to solve the task. That means, you can start at "zero" with equations derived from basic laws (KVL and KCL) or you can start - for example - with the classical equation for feedback. I prefer this way because it is straight-forward and relatively...
  13. LvW

    Op-Amp transfer function

    Hello Dan, at first, don´t be surprised if your result has a negative sign. The opamp is in inverting configuration and, therefore, the result for T(s) must also be negative. Hence, the factor k must be negative. More than that, if you have correctly written down the expression for z2/z1 (use...
  14. LvW

    Op Amp Stability

    Hi, here are some simulation results: Overshoot resulting from an input step of 1V. Opamp LF356 in buffer configuration with various feedback resistors: * Rf= 0..100 ohms : Vmax=1.1 V * Rf=1k : Vmax=1.13 V * Rf=10k : Vmax=1.4 V * Rf=10k with input compensation (5k in series with 1nF): 1.05 V...
  15. LvW

    Op Amp Stability

    Yes - for my opinion, everything you have stated in points 1) to 4) is correct. However, the main question is: Which of the various effects will dominate for a particular application? In principle, I agree also to the explanations given by you regarding limitations due to the common mode range...
  16. LvW

    Op Amp Stability

    Adam, I don´t know if the following will answer your question: 1.) I think, the main reason for using a resistor as feedback element (instead of a short) is input current compensation. In most cases the signal source connected to the non-inv. input has any internal resistance. In this case...
  17. LvW

    Op Amp Stability

    Good morning Adam, I am very sorry but until this moment I didn´t know about any message from you. Why should I ignore you? Is that the picture I have created at your side? From other forums I know that there is an e-mail if a PM is waitng for me. But I didn´t receive anything. (By the way and...
  18. LvW

    Op Amp Stability

    Ok I don't know enough about how LT Spice works in that respect, so I'll take your word for it. So basically if transient response shows oscillation then it's pointless doing an a.c analysis on the circuit. But if it is not oscillating we can still look to see how close it might be to...
  19. LvW

    Op Amp Stability

    Hi Adam, at first, a general remark to my questions: By asking "why?" I could - in most cases - imagine what you mean (for example: fc) - however, I thought it would be necessary for the reader (newcomer) to know the definition. In general, I think no symbol or abbreviation should be used in...
  20. LvW

    Current Mirrors

    Kris, I remember we had such a discussion some time ago. Hence, I do not intend to start again. However, I must admit that I cannot remember which of your questions remained unanswered. Nevertheless, I cannot resist to present a short task description of the well-known base voltage divider...
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