inverters used for what?

Discussion in 'General Electronics Chat' started by relicmarks, Oct 31, 2008.

  1. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    Do you have to adjust the trigger knob on the oscillscope to display clock signals?

    Why are the clock signals dependant on the oscilloscopes triggering?
    because the signal is toggling and not sinusoid it makes the oscilloscope display a dead signal until you adjust the triggering

    If i have a toggling pulse from low to high this is positive logic, but if i put a inverter chip than it becomes high to low which is positive logic or negative logic?

    If low to high or high to low is both positive logic, why would they be used differently? or when would you use them differently?

    whens the best function to use a inverter to reverse the polarity of a logic state? going from high to low and you want to inverter the signal to low to high? why or when do you do this?

    What would you use a inverter for to change the logic from high to low , to low to high, why or when would you use this please?
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    If your logic uses a positive voltage, it is positive logic in one sense. The transitions are always between ground and that positive voltage.

    If your logic function is to invert, like a NAND gate, it can be considered negative logic - the function is true when the output is low.

    A long time ago when the common transistors were PNP, logic was negative - the transition went from ground to -8 volts.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    It depends. Some O'scopes have an Auto trigger mode. If the channel input is AC coupled and Auto trigger mode is selected, the O'scope will generally display a decent trace. Some auto triggers will also work in DC coupled mode.

    The clock signals aren't dependent upon the O'scope triggering. The display of the clock signal on the screen of the O'scope is dependent upon the triggering.

    Try the Auto trigger mode, if your O'scope has one. If not, you'll have to adjust the trigger level manually.

    Too many questions that are extremely broad in scope for one thread.
     
  4. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    1.) The display of the clock signal on the screen of the O'scope is dependent upon the triggering.

    Yes this is what i ment , why is the clock signal dependent upon the triggering?

    2.) If the channel input is AC coupled and Auto trigger mode is selected, the O'scope will generally display a decent trace. Some auto triggers will also work in DC coupled mode.

    I thought a clock signal was DC levels so it should be DC coupled? why put it on AC coupled?

    if a clock signal AC levels since its toggling so fast for the oscilloscope?
     
  5. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    1.) If your logic uses a positive voltage, it is positive logic in one sense. The transitions are always between ground and that positive voltage.

    Yes the inverter chips just "invert the transition" not the logics polarity

    So why would i want to invert the transition or when would i use this technique of inverting the transition states?

    examples please?
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    The clock signal (in a circuit) itself is not dependent upon the O'scope triggering. But if you want to be able to display it on the screen of an O'scope, you must get the trigger level to within the + and - levels of the digital signal. If the signal is TTL, the trigger level will typically be somewhere between 0.8v and 2.8v. If the signal is CMOS, it'll be somewhere between Vss/GND and Vdd.

    2.) If the channel input is AC coupled and Auto trigger mode is selected, the O'scope will generally display a decent trace. Some auto triggers will also work in DC coupled mode.

    I thought a clock signal was DC levels so it should be DC coupled? why put it on AC coupled?[/QUOTE]
    If the signal is AC coupled, the average value of the trace on the display will be centered around 0v. Thus, a trigger level of 0v will cause a trace to sweep when the input signal transitions across 0v.

    Selecting AC input de-couples (blocks) any DC level that the input signal may have on it. However, the effects of the AC signal are passed through.
     
  7. beenthere

    Retired Moderator

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    Let's say you have a source that produces a positive clock pulse, but on chip, which has to stay synchronized with the rest of the logic, requires a negative-going clock. You get around that rorblem with an inverter, which presents that chip with a negative going clock at about the same time as the rest of the logic gets the positive going clock.
     
  8. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    1.) But if you want to be able to display it on the screen of an O'scope, you must get the trigger level to within the + and - levels of the digital signal.

    When do digital signals need trigger levels? because sinewaveforms don't need trigger levels ?


    2.) If the signal is AC coupled, the average value of the trace on the display will be centered around 0v.

    When the signal is DC coupled , what is the average value of the trace?
    where would it be centered around?

    3.) So i guess a Clock signal is AC signal since its toggling/transitioning states?

    4.) A clock signal looks ilke a squarewaveform, so i guess a squarewaveform is AC signal and not DC signal levels?
     
  9. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    1.) Let's say you have a source that produces a positive clock pulse, but on chip, which has to stay synchronized with the rest of the logic, requires a negative-going clock. You get around that problem with an inverter, which presents that chip with a negative going clock at about the same time as the rest of the logic gets the positive going clock.

    Thank you for the example, do you guys have any others please?
     
  10. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Maybe you should google what triggering actually is and how it works, that will help you a lot and answer all your questions.
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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    Digital signals don't need trigger levels - unless you wish to display them.

    Then they need to have trigger levels.
    Sine waves need triggering at appropriate levels to make sense out of them.


    When the signal is DC coupled, the input to the O'scope is absolute. There is no "averaging." That is why I suggested that you try using AC coupling. Once you get the triggering down using AC coupling, you can switch back to DC coupling, and adjust triggering for the offset.

    No. However, if you use AC coupling as input, the clock signal will transition around 0v. This assertion is true regardless of the technology involved (ie: TTL, RTL, CMOS, etc).

    Actually, you're close. :) Good on you for figuring that out.

    A square wave is the sum of all of the odd harmonics of a given frequency.

    This is very hard to understand at first.

    Wikipedia has a very good entry on this very subject.
     
  12. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
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    1.) Digital signals don't need trigger levels - unless you wish to display them.
    Then they need to have trigger levels.

    But WHY do they need trigger levels when you want to "display" them?

    2.) When the signal is DC coupled, the input to the O'scope is absolute. There is no "averaging." That is why I suggested that you try using AC coupling.

    What u mean by this averaging and absolute?

    Averaging starts the transition at Ov
    Absolute starts the transition at ?

    3.) Once you get the triggering down using AC coupling, you can switch back to DC coupling, and adjust triggering for the offset.

    Are you saying that the triggering knob doesn't work in AC coupling only in DC coupling?

    4.) I'm really confussed about if a clock signal is AC or DC, or both because a clock signal as a high frequency mostly so thats AC, but at the same time it has a low state and high state DC levels so thats DC voltages
     
  13. Audioguru

    New Member

    Dec 20, 2007
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    Hi Walters.
    Why did you change your name to Relicmarks?
     
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