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  1. R

    Question about B-E voltage.

    Do they give good reasons why? Who is suggesting that you measure and use the variation of Vbe? Perhaps qualitative knowledge is all that is needed. What is Bbr? If two transistors are made together from the same substrate, then it can be assumed that they are going to be matched and in...
  2. R

    Question about B-E voltage.

    False conclusion. Just because part of Vbe does not control the emitter-base junction does not mean all of Vbe is ineffective in controlling the Ic . Ratch
  3. R

    Question about B-E voltage.

    The above two sentences contain redundant words. They should say something like "There is a (high, strong, fast) wind here now. And "The stream from the rain runoff is rapid". I would hazard a guess that the rain is making the current in our river flow significantly faster. Indeed, I expect...
  4. R

    Question about B-E voltage.

    How do you conclude that. Without Vbe, there would not be any control voltage at all across the emitter-base junction. Just because part of the Vbe voltage is lost across the bulk resistance, does not mean that Vbe is completely ineffective. Ratch
  5. R

    Question about B-E voltage.

  6. R

    Question about B-E voltage.

    Everyone should read this link. http://cr4.globalspec.com/thread/68055/voltage-vs-current Especially posts #9 and #10. There is a lot of good info in that thread. By the way, Winfield Hill is the author of "The Art of Electronics". Observe the way he designs circuits. Interesting. Ratch
  7. R

    Question about B-E voltage.

    R = V/I and its variants is not Ohm's law. It is the definition of resistance. Ohm's law is concerned with the linearity of the resistance. Components like junction diodes do not follow Ohm's law. Other components like most resistors do (within a wide range of values). So Ohm's law is a...
  8. R

    Question about B-E voltage.

    I believe this argument in the past has reached a conclusion. Describing the operation of a BJT with respect to its physics stops the chicken and egg argument dead in its tracks. Just because a BJT is a voltage controlled current source (transconductance amplifier) does not mean that circuit...
  9. R

    Question about B-E voltage.

    I think we have two subjects being discussed. 1) Whether a BJT by itself is a current amplifier or a transconductance amplifier. 2) What are some methods used for circuit design using BJTs. Describing how a circuit is designed using a particular topology does not prove or disprove subject...
  10. R

    Question about B-E voltage.

    Correct, only the voltage across the E-B junction is effective in controlling Ic. Ratch
  11. R

    Question about B-E voltage.

    Both Ic and Ib are exponentially related to Vbe. So when you divide Ic by Ib, the exponent and Vbe cancels out, and you get a simple proportion (Beta). Then you can do whatever you want to the indicator of Ic, which is Ib, and be assured of what Ic will be. That is analogous to controlling the...
  12. R

    Question about B-E voltage.

    At the higher currents, the bulk resistance between the base and emitter contributes to the higher Vbe. Ratch
  13. R

    Question about B-E voltage.

    The BJT by itself is a transconductance amplifier. This means that the Vbe voltage controls the Ic. The nonlinearity of the curves is due to the BJT being a diffusion device. Diffusion actions produce exponential results which are nonlinear. And, the physics of a BJT and a junction diode...
  14. R

    power supply

    The components within the red circle form a half-wave rectifier. "Circuit ground" is whatever the schematic creator wants to designate as a common point to reference voltages, or where a lot of components connect together. It is a state of mind for the schematic interpreter. Sometimes an...
  15. R

    How much of a Short circuit is too much?

    You might want to peruse this thread to find out what Ohm's law really is. http://www.electro-tech-online.com/threads/ohms-law-clarification.126014/ Ratch
  16. R

    I'm fairly new to electronics, but have some idea,BUT how do these work?

    Resonance occurs when two energy storage elements, either mechanical or electrical, swap energy back and forth at a sinusoidal rate at a particular frequency. In electrical circuits, this happens when the reactance of the two elements are equal. Another requirement is that the current-voltage...
  17. R

    LC filter Circuit HELP!!

    Yes, it does. I neglected to show that the numerator term also equates to zero. Zero is the lowest value the impedance can be in a passive circuit, and infinity is the highest it can be. And, of course, you have to use the correct frequency when you solve the equations for C1 and C2. I...
  18. R

    LC filter Circuit HELP!!

    I am afraid I have led all of you astray. A parallel LC circuit does not have a equivalent series circuit. The parallel LC circuit without resistance has an infinite impedance, whereas a series circuit has zero impedance. There is just no transformation possible. I don't see how the problem...
  19. R

    LC filter Circuit HELP!!

    Keep in mind that since there is no resistance for the parallel circuit of L1 and C1, their series equivalent values will be the same as their parallel values. In other words, Ls = Lp and Cs=Cp. Ratch
  20. R

    LC filter Circuit HELP!!

    OK, here is how to do it. First find C1 in parallel with L1 using the rejection resonant frequency. I think you already did that. Then convert the parallel circuit values of C1 and L1 into series values at the acceptance frequency. Next calculate the capacitance of C2 required to make the...
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