telecombug Posted April 19, 2004 Report Share Posted April 19, 2004 hi everybody i have a project over TTL OR gate. and i wanna know about its circutry specially which transisters should i use and how much resistances should be used.........my last date of submission iz 24th april...................please help me over this project!!!!!!!!!!!!!!telecombug Link to comment Share on other sites More sharing options...
hotwaterwizard Posted April 21, 2004 Report Share Posted April 21, 2004 Here you go! Link to comment Share on other sites More sharing options...
hotwaterwizard Posted April 22, 2004 Report Share Posted April 22, 2004 Too bad your Email is hidden i could hav emailed you the schematic.Why would someone hide their Email Address? Link to comment Share on other sites More sharing options...
Kevin Weddle Posted April 22, 2004 Report Share Posted April 22, 2004 The problem with a simple gate is the slew rate. The gain is not high enough through the transition. A low to high transition will not produce a high quick enough. If you make the gain very low with a pulse input, you get a pulse output the with the same reduction that you would have with a sine wave. A reduced amplitude means a lower rate of change. Link to comment Share on other sites More sharing options...
MP Posted April 23, 2004 Report Share Posted April 23, 2004 ...except with this TTL circuit you are not worried about slew rate as the response time is only dependent upon the response of this transistor at saturation. This is plenty fast enough for TTL switching.MP Link to comment Share on other sites More sharing options...
Kevin Weddle Posted May 6, 2004 Report Share Posted May 6, 2004 You need more gain. Try using a push-pull. What an OR gate uses is a phase splitter. Which works the same as a push-pull. A push-pull is what an opamp uses. The formation of logic begins to be a little trickier, doesn't it. Link to comment Share on other sites More sharing options...
audioguru Posted May 6, 2004 Report Share Posted May 6, 2004 Hotwaterwizard,Your very nice circuit actually is RTL, not TTL. I hope that Telecombug doesn't lose marks for that oversight.Kevin,Do you see how this OR gate works? It is simply that one transistor OR the other transistor OR both transistors turn-on the LED.There is no phase-splitter. Link to comment Share on other sites More sharing options...
hotwaterwizard Posted May 6, 2004 Report Share Posted May 6, 2004 Then this one must be a DRL or Gate Link to comment Share on other sites More sharing options...
hotwaterwizard Posted May 6, 2004 Report Share Posted May 6, 2004 A real TTL OR Gate iz a bit more complicated. Link to comment Share on other sites More sharing options...
Kevin Weddle Posted May 19, 2004 Report Share Posted May 19, 2004 A phase splitter is what allows you to get high gain from the totem pole ouput. The totem pole is two NPNs. It is interesting that one NPN is setup for amplification while the other is setup as a voltage follower. I think this is because the phase splitter produces enough gain for the voltage follower. So the overall high gain is obtained from the splitter producing the high gain for the voltage follower and the totem pole ouput producing high gain. There is no doubt that the configuration was designed for handling the large signal, while providing the high gain slew for the transition. Link to comment Share on other sites More sharing options...
audioguru Posted May 20, 2004 Report Share Posted May 20, 2004 Kevin,An emitter follower has a voltage gain of 0.99 or more. It does not have a transition and its output goes from low to high just as fast as its input because its output follows its input.Any very high-speed circuit doesn't have much gain, and any very high-gain circuit doesn't have much speed. Link to comment Share on other sites More sharing options...
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