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Resistor-Transistor Logic may well have been the earliest form of transistorized digital logic, but most people tend to associate the term "RTL" with integrated circuits, and the first family of digital integrated circuits was Motorola's MECL family, introduced in 1962.
The fan-in limitation described is specific to RTL integrated circuits; the fan-in of discrete RTL circuits varies widely depending on the specific components used.
-- Brouhaha 02:04, 14 Sep 2004 (UTC)
This article needs attention from an expert in Early computers. Please add a reason or a talk parameter to this template to explain the issue with the article.(March 2009) |
This article needs attention from an expert in Electronics. Please add a reason or a talk parameter to this template to explain the issue with the article.(March 2009) |
I suspect that historically, the "3-input gate with 3 transistors" is the kind historically defined as "RTL", and the arrangement that was actually implemented. I suspect the "3-input gate with 1 transistor" view is a misunderstanding, was never actually implemented -- or if it was implemented, it wasn't called "RTL".
Could an expert clarify if a "RTL gate" always used one transistor per input, or if there were significant numbers of things built with only one transistor per gate, and that the builders actually called them "RTL gates"? -- 68.0.124.33 ( talk) 13:47, 28 March 2008 (UTC)
I think that any 3-input RTL NOR gate that uses 3 transistors is actually 3 RTL inverters with their outputs connected as a wired-AND. Otherwise you would have to say that RTL allows infinite fan-in by just adding transistors. If you limit RTL gates to 1 transistor, then you must say that an RTL gate with multiple inputs connected via a resistor network has a very limited fan-in because each input has to compete with the others. Then you can see the advantage of replacing the resistors with diodes, and understand how this leads to DTL (which is slower but allows more fan-in).
I can easily imagine RTL designers both circuits. To minimise transistors they could use one-transistor-per-gate if there are only one or two input, and multiple-transistors-per-"gate" if they more inputs required. That would explain both circuits.
60.241.12.136 ( talk) 09:59, 18 October 2009 (UTC) Computation structures
By Stephen A. Ward, Robert H. Halstead (Section 1.8.4) explains how fan-in limitations force RTL to shift from "input gating" (multiple inputs on 1 transistor) to "output gating" (1 transistor per input) "early in the history of RTL"
Google RTL "output gating" âPreceding unsigned comment added by 60.241.12.136 ( talk) 10:44, 19 October 2009 (UTC)
... So then the problem of limited fan-in can be solved by using "output gating" instead of "input gating", but doing so means you must use at least as many transisitors as you have inputs, which would have made it it more expensive than DTL back then, which only require a separate diode for each input. 14.203.83.243 ( talk) 08:00, 12 September 2016 (UTC)
It should be emphisized that the diagram is a "Simplified schematic" and does not actually work. Someone should be able to find a "published" schematic that actually works. I can only provide a design similar to those used in early computer designs. I would hate to think that some future engineer would try to build the circuit as shown and find that he wasted his time. UPCMaker ( talk) 23:02, 3 April 2008 (UTC)
If R1 returned to a negative supply it would then work. If R1 was removed and the transistor is silicon and the temperature is low enough the circuit might be workable but very slow turning off. If the transistor is germanium, R1 returning to a negative supply is needed to turn the transistor off. R3 and R4 can turn the transistor on without any help from R1 but R1 will make it difficult or impossible to turn the transistor off. R1 returning to a negative supply is needed to overcome base leakage and provide a low enough base voltage to assure the transistor is turned off especially with a germanium transistor which has high leakage and low base emitter voltage. UPCMaker ( talk) 12:44, 4 April 2008 (UTC)
It still looks like R1 returns to the plus supply not the negative supply??? UPCMaker ( talk) 00:16, 5 April 2008 (UTC)
I was seeing the old picture but now I see the correct one. Thanks! UPCMaker ( talk) 18:41, 5 April 2008 (UTC)
Some how the schematic got changed back. R1 is again returning to +V. UPCMaker âPreceding unsigned comment added by 206.53.104.196 ( talk) 17:42, 24 October 2009 (UTC)
Dicklyon, I have no any connection with this source. I realize that it is not so reputable but it is the only source giving good intuitive RTL explanations, considerations and some calculations. This was the reason for including the link. Regards, Circuit dreamer ( talk, contribs, email) 22:44, 12 October 2010 (UTC)
When was RTL invented? Dicklyon on this page is mentioning that in 1958, RTL was already around. Was RTL born in that year or before?
ICE77 ( talk) 23:59, 17 February 2011 (UTC)
Please let me know if you found out anything.
ICE77 ( talk) 16:33, 27 April 2011 (UTC)
Alright folks, thanks a lot. I guess we can say RTL has been around since at least 1956. That's all I wanted to know.
ICE77 ( talk) 05:17, 15 May 2011 (UTC)
The whole idea of "logic families" wasn't really necessary back in the days when you had to design the whole circuit from scratch using wires, resistors, diodes and transistor (or valves/tubes). It was only when they started manufacturing ICs with pre-assembled gates that it became necessary to classify them, and by that time TTL and DTL would have been the main families. Besides, in a circuit built out of discrete components, it's arbitrary whether a resistor is part of the output of one gate or the input of the following gate, so there's no hard distinction between "output-gating" or "input-gating". 14.203.83.243 ( talk) 08:10, 12 September 2016 (UTC)
I propose creating an article for RCTL for reasons of consistency. Information about RCTL is already part of this article under the section called "Speeding up RTL". I looked at http://en.wikipedia.org/wiki/Logic_family and I noticed that most subclasses of circuits are linked to specific articles (aside from RCTL which points to RTL and therefore it's inconsistent).
ICE77 ( talk) 02:27, 18 February 2011 (UTC)
I've snipped the assertion regarding threshold logic gates since it misinterprets the source. I'm familar with the Hurst book, and yes it does give a very similar circuit to that described here, but the emphasis and intent are different. The circuit described therein is an RTL example from the DONUT computer and itself is a reimplementation of a threshold gate first advanced by SC Chao in a 1959 paper in IRE Transactions on Electronic Computers. This is not even the only form of threshold gate - the Hurst book outlines a number of different approaches in the chapter referenced.
Although any Boolean gate can by definition be considered a threshold gate (since threshold gates are a superset of Boolean gates) it misses the key elements that make threshold logic distinct from Boolean logic, namely thresholds that lie conceptually between the Boolean AND and OR operations (e.g. output true if at least three of five inputs are true, instread of simply one or more [OR], or all [AND] of them), and optionally the weighting of inputs so that some inputs count for more than others. Threshold gates therefore bear more in common with artificial neurons than conventional Boolean logic gates. Crispmuncher ( talk) 15:44, 21 April 2011 (UTC)
I think it would be better to use the ASCII hyphen "-" (0x2d) instead of the Em Dash "â" (U+2013 ie. 0xe28093) in the page title.
This would make links to this page look cleaner, ie. /info/en/?search=Resistor-transistor_logic
instead of the current /info/en/?search=Resistor%E2%80%93transistor_logic
Currently, this page is at /info/en/?search=Resistor%E2%80%93transistor_logic
, and /info/en/?search=Resistor-transistor_logic
redirects to /info/en/?search=Resistor%E2%80%93transistor_logic
.
â Preceding unsigned comment added by PeterBehnam ( talk ⢠contribs) 08:52, 4 February 2022 (UTC)
This article is rated Start-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | |||||||||||
|
Resistor-Transistor Logic may well have been the earliest form of transistorized digital logic, but most people tend to associate the term "RTL" with integrated circuits, and the first family of digital integrated circuits was Motorola's MECL family, introduced in 1962.
The fan-in limitation described is specific to RTL integrated circuits; the fan-in of discrete RTL circuits varies widely depending on the specific components used.
-- Brouhaha 02:04, 14 Sep 2004 (UTC)
This article needs attention from an expert in Early computers. Please add a reason or a talk parameter to this template to explain the issue with the article.(March 2009) |
This article needs attention from an expert in Electronics. Please add a reason or a talk parameter to this template to explain the issue with the article.(March 2009) |
I suspect that historically, the "3-input gate with 3 transistors" is the kind historically defined as "RTL", and the arrangement that was actually implemented. I suspect the "3-input gate with 1 transistor" view is a misunderstanding, was never actually implemented -- or if it was implemented, it wasn't called "RTL".
Could an expert clarify if a "RTL gate" always used one transistor per input, or if there were significant numbers of things built with only one transistor per gate, and that the builders actually called them "RTL gates"? -- 68.0.124.33 ( talk) 13:47, 28 March 2008 (UTC)
I think that any 3-input RTL NOR gate that uses 3 transistors is actually 3 RTL inverters with their outputs connected as a wired-AND. Otherwise you would have to say that RTL allows infinite fan-in by just adding transistors. If you limit RTL gates to 1 transistor, then you must say that an RTL gate with multiple inputs connected via a resistor network has a very limited fan-in because each input has to compete with the others. Then you can see the advantage of replacing the resistors with diodes, and understand how this leads to DTL (which is slower but allows more fan-in).
I can easily imagine RTL designers both circuits. To minimise transistors they could use one-transistor-per-gate if there are only one or two input, and multiple-transistors-per-"gate" if they more inputs required. That would explain both circuits.
60.241.12.136 ( talk) 09:59, 18 October 2009 (UTC) Computation structures
By Stephen A. Ward, Robert H. Halstead (Section 1.8.4) explains how fan-in limitations force RTL to shift from "input gating" (multiple inputs on 1 transistor) to "output gating" (1 transistor per input) "early in the history of RTL"
Google RTL "output gating" âPreceding unsigned comment added by 60.241.12.136 ( talk) 10:44, 19 October 2009 (UTC)
... So then the problem of limited fan-in can be solved by using "output gating" instead of "input gating", but doing so means you must use at least as many transisitors as you have inputs, which would have made it it more expensive than DTL back then, which only require a separate diode for each input. 14.203.83.243 ( talk) 08:00, 12 September 2016 (UTC)
It should be emphisized that the diagram is a "Simplified schematic" and does not actually work. Someone should be able to find a "published" schematic that actually works. I can only provide a design similar to those used in early computer designs. I would hate to think that some future engineer would try to build the circuit as shown and find that he wasted his time. UPCMaker ( talk) 23:02, 3 April 2008 (UTC)
If R1 returned to a negative supply it would then work. If R1 was removed and the transistor is silicon and the temperature is low enough the circuit might be workable but very slow turning off. If the transistor is germanium, R1 returning to a negative supply is needed to turn the transistor off. R3 and R4 can turn the transistor on without any help from R1 but R1 will make it difficult or impossible to turn the transistor off. R1 returning to a negative supply is needed to overcome base leakage and provide a low enough base voltage to assure the transistor is turned off especially with a germanium transistor which has high leakage and low base emitter voltage. UPCMaker ( talk) 12:44, 4 April 2008 (UTC)
It still looks like R1 returns to the plus supply not the negative supply??? UPCMaker ( talk) 00:16, 5 April 2008 (UTC)
I was seeing the old picture but now I see the correct one. Thanks! UPCMaker ( talk) 18:41, 5 April 2008 (UTC)
Some how the schematic got changed back. R1 is again returning to +V. UPCMaker âPreceding unsigned comment added by 206.53.104.196 ( talk) 17:42, 24 October 2009 (UTC)
Dicklyon, I have no any connection with this source. I realize that it is not so reputable but it is the only source giving good intuitive RTL explanations, considerations and some calculations. This was the reason for including the link. Regards, Circuit dreamer ( talk, contribs, email) 22:44, 12 October 2010 (UTC)
When was RTL invented? Dicklyon on this page is mentioning that in 1958, RTL was already around. Was RTL born in that year or before?
ICE77 ( talk) 23:59, 17 February 2011 (UTC)
Please let me know if you found out anything.
ICE77 ( talk) 16:33, 27 April 2011 (UTC)
Alright folks, thanks a lot. I guess we can say RTL has been around since at least 1956. That's all I wanted to know.
ICE77 ( talk) 05:17, 15 May 2011 (UTC)
The whole idea of "logic families" wasn't really necessary back in the days when you had to design the whole circuit from scratch using wires, resistors, diodes and transistor (or valves/tubes). It was only when they started manufacturing ICs with pre-assembled gates that it became necessary to classify them, and by that time TTL and DTL would have been the main families. Besides, in a circuit built out of discrete components, it's arbitrary whether a resistor is part of the output of one gate or the input of the following gate, so there's no hard distinction between "output-gating" or "input-gating". 14.203.83.243 ( talk) 08:10, 12 September 2016 (UTC)
I propose creating an article for RCTL for reasons of consistency. Information about RCTL is already part of this article under the section called "Speeding up RTL". I looked at http://en.wikipedia.org/wiki/Logic_family and I noticed that most subclasses of circuits are linked to specific articles (aside from RCTL which points to RTL and therefore it's inconsistent).
ICE77 ( talk) 02:27, 18 February 2011 (UTC)
I've snipped the assertion regarding threshold logic gates since it misinterprets the source. I'm familar with the Hurst book, and yes it does give a very similar circuit to that described here, but the emphasis and intent are different. The circuit described therein is an RTL example from the DONUT computer and itself is a reimplementation of a threshold gate first advanced by SC Chao in a 1959 paper in IRE Transactions on Electronic Computers. This is not even the only form of threshold gate - the Hurst book outlines a number of different approaches in the chapter referenced.
Although any Boolean gate can by definition be considered a threshold gate (since threshold gates are a superset of Boolean gates) it misses the key elements that make threshold logic distinct from Boolean logic, namely thresholds that lie conceptually between the Boolean AND and OR operations (e.g. output true if at least three of five inputs are true, instread of simply one or more [OR], or all [AND] of them), and optionally the weighting of inputs so that some inputs count for more than others. Threshold gates therefore bear more in common with artificial neurons than conventional Boolean logic gates. Crispmuncher ( talk) 15:44, 21 April 2011 (UTC)
I think it would be better to use the ASCII hyphen "-" (0x2d) instead of the Em Dash "â" (U+2013 ie. 0xe28093) in the page title.
This would make links to this page look cleaner, ie. /info/en/?search=Resistor-transistor_logic
instead of the current /info/en/?search=Resistor%E2%80%93transistor_logic
Currently, this page is at /info/en/?search=Resistor%E2%80%93transistor_logic
, and /info/en/?search=Resistor-transistor_logic
redirects to /info/en/?search=Resistor%E2%80%93transistor_logic
.
â Preceding unsigned comment added by PeterBehnam ( talk ⢠contribs) 08:52, 4 February 2022 (UTC)