What is TTL logic?

Discussion in 'General Electronics Chat' started by Vladimir Tess, Aug 31, 2007.

  1. Vladimir Tess

    Thread Starter New Member

    Aug 29, 2007
    Hey guys,

    You see, I am reading this book, "digital electronics" -- the demystified version. Where I am reading is on section "Logic Gate input and Output". I've added here one of his page without permission (i gotta get this one), so can you please help me understand what he means by that diagram? How do these input gates work.

    I understand the concept of NPN transistors.

    Thanks much,

    Vlad Tess
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    Have you looked into the Ebook on this site? Specifically this section - http://www.allaboutcircuits.com/vol_4/chpt_3/1.html. It should answer your question.

    I assume this is a learning exersize - the function of a logic gate may be understood without any knowledge of the internal circuit.
  3. Dave

    Retired Moderator

    Nov 17, 2003
    If this is copyrighted material can you either obtain permission from the owner, else remove the zip-file and paraphrase the relevant sections. Thank you.

  4. Vladimir Tess

    Thread Starter New Member

    Aug 29, 2007
    I don't... know how to remove the zip file. I don't see any option to do so. Please admin, remove it for me.

  5. hgmjr

    Retired Moderator

    Jan 28, 2005
    I removed the attachment as you requested.

    There is a means for you, the poster, to remove it as well. Just open your post up for "edit" that contains the attachment and select "advanced edit". You then scroll down to the "manage attachments" section and click on the "manage attachments" button. You will then get a window in which you will see a "remove" button. Click on the button to remove the attachment.

  6. Newton1Law


    Aug 22, 2007
    TTL Logic - Transistor Transistor Logic if this helps. It usually refers to the type of switchs (in this case transistor to transistor) used to obtain an output. AND gate, OR, NOR, NANAD, etc. In each case you are switching transistors from one state to another.
  7. Omega blood

    New Member

    Sep 5, 2007
    I will add to this;
    It's a group of IC's used to perform digital functions. Some containing many logic gates, digital to analog converters Ect...

    For example you can use the 7400 series of TTL IC's to build a digital clock like the one that wakes you up in the morning. :cool:
    You can make all sorts of neat things with them.
  8. Papabravo


    Feb 24, 2006
    TTL was named by comparison to its predecessors DTL (Diode Transistor Logic) and RTL (Resistor Transistor Logic). In TTL you have both the input circuit built from transistors and the output circuit built from transistors. There are very few explanations extant on the multi-emitter transistors used in TTL logic input circuits. As others have noted it is possible to spend a whole career designing with these parts and never understand the operation of this part of the circuit. What is important to understand is that TTL inputs source current and you must pay attention to fan-out whenever an output has to drive more than a few inputs. CMOS circuits have largely eliminated such considerations, but have introduced a whole new range of gotchas.