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  1. R

    Determine the Vcbo of a germanium transistor and the voltage drop along the connected components.

    Right now, with that high base resistance (100 k) in Q1, almost all the Icbo will go through the base-emitter junction of Q1, and get betatized into a much larger current. You should take out Rb, and put in an emitter resistor Re. The emitter resistor will look like (beta+1) Re from the base...
  2. R

    Phase shift oscillator help

    See my answer to the Electrician. Ratch
  3. R

    Phase shift oscillator help

    I looked up some references, and they appear to agree with you that only the transfer function should be used to determine oscillation frequency. It appears that I was wrong about that. Sorry for the confusion. Ratch
  4. R

    Phase shift oscillator help

    Ok, it is easy to do, but upon thinking about it, I don't think it proves anything to look at the absolute and argument values of all the terms gathered on the right hand side or left hand side. Yes, and the freq of oscillation where the phase is 0 can change when the r2 changes. I beg to...
  5. R

    Phase shift oscillator help

    You are plotting a term called "t". You should be plotting the equation of " t = 1" . Ratch
  6. R

    Phase shift oscillator help

    Look at the 3rd line from the bottom of the attachment which says t = 1 Ratch
  7. R

    Phase shift oscillator help

    Didn't I answer that concern in post #28 ? Didn't you understand my answer? Ratch
  8. R

    Phase shift oscillator help

    No so. In my post #14, I show that the term you mentioned is equated to 1, so R2 cannot be factored out. It is included in the equation for omega. Ratch
  9. R

    Determine the Vcbo of a germanium transistor and the voltage drop along the connected components.

    What are you trying to do with this circuit? Icbo is a internal current generator within the collector slab that is controlled by the temperature of the slab and powered by the collector-base voltage. You cannot turn it on or off. You can only design around it. Why are you using a germanium...
  10. R

    Phase shift oscillator help

    You got the gain and frequency. What else do you need? What is T(s)? There is a lot of textual material on how those equations are derived. Why do it again? Ratch
  11. R

    Phase shift oscillator help

    Not so, see below. Yes, I did. See below. Not so, see below. Yes, my last equation in post #14 is correct, See below. OK, here is my take on this. I set up an equation based on the assumption that the closed loop gain of the circuit had to be at least 1 in order to oscillate. I don't...
  12. R

    Phase shift oscillator help

    Correct, but they are not independent of each other. No, the components (R2) in the last amp also change the phase, That is because the last amp is amplifying a complex signal. The different amplification values caused by varying R2 can change the proportion of imaginary values to real...
  13. R

    Phase shift oscillator help

    Perhaps so, but not necessary. We both derived, by other means, that R2/R needs to be minimum of 8 to barely sustain oscillation. Now, we can crank the R2 even high like 15*R. The frequency will change and the higher amplification will drive the amps into saturation. But, if we put a resistor...
  14. R

    Phase shift oscillator help

    My derivation in post #14 shows that R2 affects both the frequency and the gain. Show me where I went wrong. Ratch
  15. R

    Phase shift oscillator help

    I agree with what you say about introducing nonlinearity to stabilize the oscillator. Yes, the amplifier chain in this circuit has to amplify a little greater than 1 to get started. Then whatever nonlinearity you have built into the circuit can take over and stabilize the oscillator. My...
  16. R

    Phase shift oscillator help

    Nope, you still have not looked at my derivation at post #14. I use the same term, but I set it to 1, which is the gain of the amp chain. That means that R2 cannot be ignored, and is a frequency determining element because it changes the phase. Ratch
  17. R

    Phase shift oscillator help

    Yes, I agree with your analysis. Using Steinmetz notation, the gain of the first two amps is (1/4)/_-120°. The gain of the last amp is -R2/(R+sqrt(3)*R*j) . Multiplying the gains together and setting them to 1 gives [(1/4)/_-120°][-R2/(R+sqrt(3)*R*j)] from which R2/R = 8 Ratch
  18. R

    Phase shift oscillator help

    Your equation for omega at oscillation is wrong. R2 is not in your formula, but it should be because it affects the zero phase shift. What rational can you give for giving the real parts of the expression any value? You need to set the imaginary parts of the loop equation to zero so there is...
  19. R

    Phase shift oscillator help

    Yes, please show it. My derivation above shows how I did it. I would like to see the calculation for R2/R = 8, Ratch
  20. R

    Phase shift oscillator help

    Please bear with me because I have never done this before. First, one has to decide whether one is building an amplifier or an oscillator. The circuit above shows three amplifiers in series, each of which change the phase of the signal. The rc in the first amplifier changes the phase -60°...
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