Transistor ComputeR

Discussion in 'General Electronics Chat' started by Robin Mitchell, Jan 25, 2011.

  1. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
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    Hi everyone,
    I have a question,

    If i where to build glue logic using transitors would the transistors need resistors on their bases because all of the CPU schematics i have seen suggest that they dont. Just shows the output of one gate connecting directly to the input of an other (output of transistor to base of transistor)?

    I think it should because the base current cant be more than 5mA anyway so surely it would damage the transistors :p

    Thanks
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Take another look at the RTL gates I showed you. Any direct connections did not need base resistors, the collector resistors did double duty. You need the base resistors where the circuits are feeding to the outside world, such as switches. I figured all resistors as 10K, the original RTL gates used 3.6VDC for the power supply.

    The classic 1/10 current on base to collector currents for saturation rule of thumb applies.
     
    Robin Mitchell likes this.
  3. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
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    once again, another usefull post by my nbf XD
    thanks, will do right now!
     
  4. Papabravo

    Expert

    Feb 24, 2006
    10,145
    1,791
    One other thing to watch out for is the use of MOSFETs on a silicon die to act as resistors. This is especially true if you start plying with custom silicon layout and development tools. I'm sure you'll be there soon enough.

    If you can lay your hands on it "VLSI Design" by Mead and Conway (ca. 1980) is an excellent introduction if a bit dated by this point.
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    The old Univacs I worked on had just over 10,000 discrete transistors. They were DTL logic with PNP germanium transistors. The circuit boards were all the same size, and held one to three logic elements. Seymour Cray himself did the initial designs.
     
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