Search results

Search Forums New Posts
  1. K

    transmission lines

    Corroboration on a few things would be appreciated. A transmission line can appear to the source as a parallel resonant circuit, a series resonant circuit, a capacitor, or an inductor. When constructed correctly, the source only sees a very high resistive impedance.
  2. K

    a very simple FM Tx

    How do you know you have crossed the finish line with an oscillator? I seem to think that general test lab equipment cannot tell the whole story. I cannot believe these mass produced behemoth bluetooths with Intel Pentium 4's and Windows spyware can measure accurately enough for me. If you know...
  3. K

    a high pass filter question

    Take some transistors and drive a 50 ohm load. I want the gain to be about 200. I want 1Vpp on the load. I want the signal source to be an oscillator. It'll be a very long circuit. Increase the load to 1Kohm, and it will be a lot easier. So, throw in a low resistance "anywhere", and it will be...
  4. K

    BJT biasing

    If you drive a very small signal into a transistor, and don't change the current well, the results could be weird. If you run the right change in current, information can be extracted. I think we amplify signals to enlargen our view of what has taken place.
  5. K

    a high pass filter question

    From what I have seen, it's hard to get gain. Or it's hard to develop the voltage. Or the impedance is reduced, setting up low gain for the previous circuit. Picking up the gain is difficult when the resistance is lowered. Our goal is amplification.
  6. K

    spectrum analyzers

    I wanted to make a high frequency dual slope A/D one time. I found the counters available were a little slow. Does event capture on an analyzer make use of an A/D? If so, how is it done?
  7. K

    a high pass filter question

    I always end up with a bunch of different supply voltages when designing circuits on paper. I think a lot of circuit values are chosen because of constraints. Throw a low value resistance anywhere in the circuit, and it will be seen all the way back to beginning of the circuit.
  8. K

    BJT biasing

    Does low current biasing have more to do with transistor longevity? I don't think so, because I have seen transistors biased at low current but a high VCE. I plotted beta one time, and I think it goes like this : Increase the current from zero and the beta goes high, very high. Approach about...
  9. K

    220 volts Versus 120 volts

    I believe you can take (2) out of phase sinewaves to make 220Vac. Anybody ever done this? Or do all houses come with a 220Vac line?
  10. K

    series RC circuit

    I think also that this is where theory leaves electronics. An oscillator fabricated from electronic circuits will produce harmonics, but a perfect sine on paper has none.
  11. K

    series RC circuit

    I know any waveform can be duplicated with sinewaves of various phase freqeuncy, and amplitude. Maybe harmonics is the wrong language here. I'm looking at a sinewave which approaches zero rate of change. It does this gradually. So maybe it does not have harmonics, but it does have a lot of...
  12. K

    opamp phase compensation

    Maybe I'm off, but I think your saying the cap is there for prevention, should a high frequency occurance trigger an oscillation. Though my book suggests that it's also used to extend the 20db/decade open loop rolloff, which is more stable than the 40db/decade rolloff found as you increase the...
  13. K

    series RC circuit

    If a triangle produces stronger harmonics than a sinewave, the measuring device would not be accurate.
  14. K

    opamp phase compensation

    I've read the cap can be put input to ground. To start, I'm not attempting open loop gain at all. Now, if I'm applying a high frequency that may cause excessive phase shift, why wouldn't I just select the correct gain and avoid adding the capacitor. I'm not trying to avoid a high frequency, I...
  15. K

    series RC circuit

    Anybody ever notice that if you apply, let's say a triangle, to a series RC circuit, the rate of change of voltage on one side of the capacitor is different from the rate of change of voltage on other side because of reduced amplitude? Even phase shift can't correct this. This means the...
  16. K

    opamp phase compensation

    Does the phase comp. capacitor placed at the input reduce the capacitance because it's in series with the BC capacitance of the opamp transistors? The opamp in general kind of bewilders me because of the feedback resistors dictating exact gain and handling all the current. So I would not be...
  17. K

    Tank ckt

    Thanks for leading me in the right direction concerning the first question. I had hoped a larger reactance might mean a higher impedance. Kind of disappointing. I don't like the second answer either. I was hoping it would just pull away from the supply voltage. Oh well.
  18. K

    Feats of engineering?

    I ran the same low frequency square wave into a two input gate expecting complete cancellation on the output. However, the latch I had on the output would always set. It appears there was enough offset through the gate to cause a pulse. Does that sound like the problem?
  19. K

    Tank ckt

    When calculating a tank, does the high impdeance differ if Xc=Xl=50 ohms from Xc=Xl=100 ohms? When you connect the tank at the collector of a transistor, at DC the collector is at the supply voltage. When you apply the signal, does the peak hit the supply voltage, then go down from there with...
  20. K

    High frequency A/D

    How do you digitize high frequency? I was going to use a counter based A/D, but the counters available are too slow.
Top