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transistor base load

Discussion in 'General Electronics Discussion' started by ratstar, Oct 22, 2020.

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  1. ratstar

    ratstar

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    I know I said I wasn't going to say anything, but this is a technical question, I was just wondering if you can use a 100k load on a transistors base, and it could still fire.

    Im asking because I want to make a 1 wire 100kOhm delay line (1 full second delay) and i was wonder if the transistor would fire on the other side.
     
  2. AnalogKid

    AnalogKid

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    Don't know what you mean by "fire".

    The base current in a transistor configured as a saturated switch (just guessing that that is what you are after) is dependent on the value of the base resistor, and the voltage driving the other end of the resistor. Whether or not that produces enough collector current to be useful depends on the collector load and the application for the circuit.

    Your question has almost zero useful information. Please consider providing some.

    ak
     
  3. ratstar

    ratstar

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    Aug 20, 2018
    [mod edit: Image not appropriate -> deleted]


    Given a practical amount of power, is 100k too much of a resistor to apply to the base of a transistor?

    I'm guessing it is highish, but its not too much. It still works. But would it need 2 in a cascade?
     
    Last edited by a moderator: Oct 22, 2020
  4. Nanren888

    Nanren888

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    Load? So you mean shunt? It is across the base to emitter?
    .
    Or do you mean in series with the base?
    Ohm's law and some spec for the transistor will sort out whether you will get what you want. Or explain a bit more and we might be able to help.
    Ohm's law will get you some relationshipd between resistance and voltage and current, hence power.
    FETs don't need much current. If it's series a FET might help.
    .
    Can you sketch a schematic? Otherwise we're sort of guessing what you mean. Including the gun, by the way. No clue what was meant by that.

    Was the transistor to be in its linear region, that is, analogue outputs, or acting as a switch?
     
  5. ratstar

    ratstar

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    Have you ever put a 100k resistor before the base of a transistor before? yes or no.
     
    Last edited: Oct 22, 2020
  6. Alec_t

    Alec_t

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    Yes, I have.
     
    ratstar and hexreader like this.
  7. AnalogKid

    AnalogKid

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    Yes, but not to switch 250 watts.

    ak
     
    ratstar likes this.
  8. ratstar

    ratstar

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    Aug 20, 2018
    gratzie.
     
  9. Nanren888

    Nanren888

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  10. davenn

    davenn Moderator

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    A resistor on its own isn't going to produce a delay line
     
    Martaine2005 likes this.
  11. AnalogKid

    AnalogKid

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    What type of signal are you trying to delay?
    Audio / Video / EKG / serial data / servo control / ???
    Voltage p-p
    Current
    Frequency

    ak
     
  12. Alec_t

    Alec_t

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    Given the propagation speed of an electrical signal in a wire is about 90% of the speed of light you will need a wire ~270,000km long. :D
     
    Martaine2005 likes this.
  13. bertus

    bertus Moderator

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  14. Nanren888

    Nanren888

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    There was once a delay line that was acoustic with a relatively high impedance, hence not impossible.
    Or he could mean something completely different.
    .
    But, I think most of all, we are trying too hard.
    The original poster does not seem to want to add description. Such description would allow help that was actually aligned with what he wanted to do or know.
    Multiple people have tried to ask questions that might lead to understanding.
    In the end it's the original poster's choice to not add enough detail to this.
    Maybe he's off studying at this point and will come back with more.
     
  15. ratstar

    ratstar

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    Aug 20, 2018
    woah thanks for responses!

    Sorry I dont mean a second, I meant a 2000th of a second - but it is still very long. I was going to print it out with my 3d printer, a big long zigzagging volumetric tunnel, and fill it up with water or conductive paint.

    But that would mean id have to use a bad conductor, poking magnet wire down there wouldnt work, the water is higher resistance, but the electricity travels slower through it, or use conductive paint and it would be ~25x times better overall. But it wouldnt be a kilohm resistance then, it would be a gighohm. But I figure, if your average multimeter is a megohm impedance, maybe the delay could still work with a bad conductor.
     
    Last edited: Oct 24, 2020
  16. AnalogKid

    AnalogKid

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    Using a very long wire of ***any*** type to achieve a 500 us delay is not just impractical, it's basically impossible. At c that is 5.9 million inches. At 0.7c (a common value for coax cable) you're still at over 4 million inches.
    [QUOTE="ratstar, post: 1804825, member: 53301"But that would mean id have to use a bad conductor[/QUOTE]
    No, it doesn't. The resistance of a conductor has no direct relationship with the propogation delay through it. In other words, "bad" conductors are not necessarily slower.

    A resistor-capacitor or inductor-capacitor network can be used as a delay line.
    https://en.wikipedia.org/wiki/Analog_delay_line
    https://en.wikipedia.org/wiki/Delay_(audio_effect)

    Again, answer the questions in post #11. There are many ways to delay a signal, but they don't all work with all signals.

    If all you want to do is delay when a transistor turns on after a control voltage is sent to it, that is very simple to do. But you'll never know unless you answer some questions and give us some information.

    ak
     
  17. ratstar

    ratstar

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    Aug 20, 2018
    If you have a large spool of magnet wire, and you get both ends of it free some how, you might get a readable delay out of that?
     
  18. Nanren888

    Nanren888

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    What's your plan for using the delay?
     
  19. ratstar

    ratstar

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    I was going to make a delay line memory with it, for a delay line computer. but your average 20 megahert transistors make it not very good an option, I compute the pulses down the line are way too thick to make it worthwhile, it would be about 500 metres per pulse, not very good.
     
  20. Nanren888

    Nanren888

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    Have seen an ages old calculator that used an ultrasonic delay line for memory.
    Faster RF transistors?
    Audio circuits routinely implement delays. Could google that avenue?
     
    ratstar likes this.
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