Timeline for How are logic gates created electronically?
Current License: CC BY-SA 3.0
21 events
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| Apr 14, 2021 at 21:02 | comment | added | Brian Cannard | "The pass-transistor logic (PTL) is a better way to implement circuits designed for low power applications. The low power pass-transistor logic and its design analysis procedures were reported in [12, 13]. Its advantage is that one pass-transistor network (either pMOS or nMOS) is sufficient to implement the logic function, which results in lower number of transistors and smaller input load. Moreover, direct -to-ground paths, which may lead to short-circuit energy dissipation, are eliminated." hindawi.com/journals/vlsi/2012/173079 | |
| Feb 15, 2017 at 10:56 | history | edited | KeyC0de | CC BY-SA 3.0 |
deleted 1 character in body
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| Feb 15, 2017 at 10:48 | history | edited | KeyC0de | CC BY-SA 3.0 |
deleted 1 character in body
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| Apr 22, 2014 at 22:47 | comment | added | apalopohapa | @placeholder Thanks. Just to clarify, we were talking about the OR gate that uses a TG plus a transistor. It seems that the NMOS should be a PMOS in order to let the full voltage of A=1 through. | |
| Apr 22, 2014 at 21:56 | comment | added | placeholder | @apalopohapa fixed the NOR gate as I had the wrong polarity for /A input. /A is right. The cell can present a heavy load whereas a normal cell will only look capacitive. However, normal logic gates also have shoot through current (NMOS and PMOS drive conflict) so this is not unusual. What is true though is that you cannot cascade these devices (unless you can ensure that the low impedance drive ripples through) and they can be potentially slower as there is an additional channel length that is driven through. | |
| Apr 22, 2014 at 20:27 | history | edited | placeholder | CC BY-SA 3.0 |
fixed NOR in TG series
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| Apr 22, 2014 at 19:12 | comment | added | supercat | BTW, I designed a BJT-based XOR gate to control my dad's trailer's lights back around 1977 (left light = left blinker xor brake; right light = right blinker xor brake); it was conceptually a lit like the transmission-gate XOR which btw works better in NMOS than CMOS. | |
| Apr 22, 2014 at 19:10 | comment | added | supercat | @apalopohapa: Hmm... maybe one could replace the top NFET with a PFET controlled by /A, though in that case the source of the PFET may as well connect to VDD rather than to A. | |
| Apr 22, 2014 at 18:36 | comment | added | apalopohapa | @supercat Thanks for the response. The circuit doesn't look right though, not even with the /B at the NMOS gate: When A=1, the bottom TG is off, so the only way to get a 1 at the output is through the NMOS. But the NMOS can only do so much to let 1s through. So it seems it should be a PMOS with /A at its gate. Regardless, I acknowledge the backdriving issues (thanks for the explanation). | |
| Apr 22, 2014 at 17:15 | comment | added | supercat | @apalopohapa: The biggest side-effect is that TG logic circuits can sometimes back-drive their inputs, at least momentarily. I think the "/A" at the top of the "TG" or implementation should be "/B". Assume that's the case, and both A and B start out low. Initially, A and B will be connected to the output and thus to each other. If a rising edge on A occurs before a falling edge on /A, then current from A will be able to flow back out to B. Such back-flows, even if they are brief, can cause undesired circuit behaviors. | |
| Nov 9, 2013 at 19:56 | comment | added | apalopohapa | What are the 'serious side effects' of the TG OR implementation? | |
| Mar 15, 2013 at 20:43 | comment | added | supercat |
It's worthwhile to note that many situations require a function to NAND together the outputs of a few OR gates, or NOR together the outputs of a few NAND gates. An expression like (A or B) nand (C or D) may be implemented in a single level of logic using eight transistors--much more efficiently than using two full-fledged "or" gates and NAND'ing the result.
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| Mar 15, 2013 at 20:35 | history | edited | NickHalden | CC BY-SA 3.0 |
Added pass-transistor-logic
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| Jan 7, 2013 at 12:39 | history | edited | user17592 | CC BY-SA 3.0 |
nicer truth tables
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| Jan 7, 2013 at 8:41 | vote | accept | user17534 | ||
| Jan 7, 2013 at 1:31 | comment | added | wim | Super answer!!! | |
| Jan 7, 2013 at 0:47 | history | edited | placeholder | CC BY-SA 3.0 |
typos, spelling and added in AO gate
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| Jan 6, 2013 at 21:11 | history | edited | placeholder | CC BY-SA 3.0 |
added in TG based stuff
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| Jan 6, 2013 at 20:20 | comment | added | placeholder | I wrote it myself because EE.SE is meant to be self contained and links are generally frowned upon. Additionally, I turned it into a community wiki so in the future cool ideas can be collected in here. | |
| S Jan 6, 2013 at 20:15 | history | answered | placeholder | CC BY-SA 3.0 | |
| S Jan 6, 2013 at 20:15 | history | made wiki | Post Made Community Wiki by placeholder |