Search results

  1. LvW

    Help to solve Operational amplifier

    With the exception of task 4 I do not understand any of the other tasks. It seems necessary to have some additional explanations.
  2. LvW

    LC filter Circuit HELP!!

    Ratch - congratulations. I did not think of this tricky parallel-to-series transformation. But now I remember the two resonant frequencies of a crystal - it is a similar case.
  3. LvW

    LC filter Circuit HELP!!

    The transfer function is defined as the ratio voltage output (across the R) to voltage input. Hence, it is nothing else than a (complex) voltage divider. Having the transfer function, you can see what you have to do (selecting component values) in order to fulfill the requirements.
  4. LvW

    LC filter Circuit HELP!!

    And what is the problem? If you are familiar with the rules for analyzing such circuits, why don`t you calculate the transfer function?
  5. LvW

    LC filter Circuit HELP!!

    Each filter needs a pair of input nodes and a pair of output nodes. I only can assume where the input/output could be. More than that, the question is not clear (cannot be fully identified in the jpg file). Question: Are you familiar with (a) rules for voltage dividers and (b)...
  6. LvW

    LC filter Circuit HELP!!

    The shown circuit does not work as a filter. There is no closed current loop and, hence, input voltage=output voltage.
  7. LvW

    Simple LC Oscillator

    An LC tank circuit is not an oscillator because of unavoidable resistive losses within the circuit. You neeed an amplifier.
  8. LvW

    Simple LC Oscillator

    Input? An oscillator does not have any input (just DC supply). More than that, there are many different LC oscillator topologies. Show us your circuit.
  9. LvW

    Wien Bridge Oscillator

    Very inportant question: Tunable between 10k and 50k ?
  10. LvW

    Stabilising wienbridge sine wave using FET

    Yes - for my feeling, the WIEN type oscillator is very easy to understand. However, designing a good and effective amplitude stabilization mechanism could be an challenging task. Of course, a pair of diodes across the feedback resistor will "work" - however, the situation changes if we require a...
  11. LvW

    Stabilising wienbridge sine wave using FET

    OK - accepted.
  12. LvW

    Stabilising wienbridge sine wave using FET

    Thank you for your kind advice. Just as a background information: I have written a textbook on filters and oscillators. A lack of knowlege is never a problem, if one is able to accept some comments/corrections. Do you have a good feeling while saying that you understand the circuit? I must...
  13. LvW

    Stabilising wienbridge sine wave using FET

    Are you really? Did you try? My recommendation: Do not blindly trust every circuit you find in a "text". Furthermore - do you know that the opamp input resistance may be regarded as (nearly) infinite? In case you know that - what do you think is the current through R3? Did you ever try to...
  14. LvW

    Stabilising wienbridge sine wave using FET

    The circuit - as shown - will not work. The feedback network is not correct - the FET acts as a load to the opamp and not as part of the feedback path.
  15. LvW

    Stabilising wienbridge sine wave using FET

    For low voltages betqween D and S (VDS lower than app. 0.5V) the FET works as a voltage-controlled resistor (in both directions!). In any case, you should combine the FET with another series resistor so that the voltage VDS remains within the mentioned limits. I would not use a light bulb for...
  16. LvW

    Stabilising wienbridge sine wave using FET

    Yes - the source must be grounded because the voltage VGS is the controlling quantity. However, do you know that a diode alone is not sufficient for controlling the gate voltage? You need a loading capacitor and a resistor which allows deloading.
  17. LvW

    Lots of transistors. What do they all do! (schematic)

    I would recommend to start improving your knowledge with some simpler circuits (basic amplifier circuits with one transistor, differential amplifier,...).
  18. LvW

    Differential amplifiers - why amplify the difference?

    The most important property of a diff. amplifier is that the signal output at one collector node is (a) in phase with the input signal at the other transistor and (b) inverted with respect to the "own" input signal (as in a common-emitter stage). Now - such an diff. amplifier is ALWAYS the input...
  19. LvW

    tuned (tank) circuit, oscillator, Q

    I do not intend to enter the discussion regarding the current (circulating yes/no). However, a short answer to the Q value of the LC tank. Yes - in general, we prefer a high Q value for the following reason: The phase slope of the tank is proportional to the Q value - and we prefer a high phase...
  20. LvW

    eMOSFET and common emitter amplifier

    Colin, of course, I know what you mean. However, I doubt if the questioner (a newcomer?) will be able to follow you. At first, you should mention the fact that the base current was neglected in your calculation. More than that, it is not the base voltage that "puts" 1.6V on the emitter. It is...
View older results
Top