General timing question

Discussion in 'General Electronics Chat' started by Brass, Jan 31, 2009.

  1. Brass

    Thread Starter Member

    Oct 13, 2006
    14
    0
    Hello,

    I have been reading about the speed of various IC's and was wanting to inquire would I get any more speed out of the circuit using the electrical circuit as found here?

    http://www.ehobbycorner.com/images/discrete_logic_and.gif

    OR

    Would the appropriate AND gate from the 74Fxx series be faster?

    Does it make any difference in circuit timing at all?

    Thanks in advance.



    Thanks bill for the response, if I remember correctly the datasheet for the 74Fxx states it will switch at a rate of 75Mhz would a Shottky diode be faster than that? ( Sorry I dont have a scope yet ).

    Thanks for the response studiot.

    Sorry if this sounds a bit thick but I'm still lost for an answer, which would be able to run faster the 74Fxxx or the shottky diode setup that was mentioned. This will affect part of a design descision for building a CPU from scratch and I really would like to get it right.

    Thanks in advance.
     
    Last edited: Jan 31, 2009
  2. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Depends on the diodes. And the source driving them.

    Basically a diode gate is passive, passive tends to mean higher capacitance and possibly inductance, which slows things down. You could use Schottky diodes, which will do two things, improved diode switching speed and reduce the voltage drop loss associated with diodes.

    I use diode gates all the time, since they tend to make laying out a board easier overall. If they work in the application, well, my tag states my POV.
     
  3. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    One thing to remember about speed.

    Current drain increases with speed. All the ordinary and low current versions draw pretty much the same current above 50Mhz.
     
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