Please see this image. As you can see from 0 to 999mV the output should be 0 to 100mV(this can be achieved easily) but when the input changes from 999 to 1000 and further the output should be from 10mV to 100mV. Any reference is appreciated.
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- \$\begingroup\$ @Transistor I think this might simply be a bug of the new markdown engine of SE, it requires an empty line between content and URL lists. \$\endgroup\$Marcus Müller– Marcus Müller2020-09-08 17:02:24 +00:00Commented Sep 8, 2020 at 17:02
- \$\begingroup\$ First see if you can notice the pattern in the input specification. Then identify steps that will allow you to accomplish the task. Then design circuitry fer each step. \$\endgroup\$user16324– user163242020-09-08 17:02:33 +00:00Commented Sep 8, 2020 at 17:02
- 2\$\begingroup\$ Why do you want this? The problem and the no-MCU restriction seem absurd, you're going to have to justify the need, and in so doing will reveal clues key to either selecting an actually viable solution, or rejecting the entire idea as unsound. \$\endgroup\$Chris Stratton– Chris Stratton2020-09-08 17:06:07 +00:00Commented Sep 8, 2020 at 17:06
- \$\begingroup\$ Dear Chris, using a mcu is easy but how to do it in old fashioned way, i want to know it...by the way this is used for 7017 IC. \$\endgroup\$Raj Kiran– Raj Kiran2020-09-08 17:08:59 +00:00Commented Sep 8, 2020 at 17:08
- 2\$\begingroup\$ Why would you want to know how to do something that makes no sense for noise reasons? Either, this is an XY problem (i.e. you think this is a solution to a problem you're not telling us about, but it's actually not a solution at all), or you're trying to distract from the fact that this is homework. \$\endgroup\$Marcus Müller– Marcus Müller2020-09-08 17:11:10 +00:00Commented Sep 8, 2020 at 17:11
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2 Answers
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5 Here is a conceptual diagram. This is not a real schematic. It is just to give you the idea. There are many problems with this idea that others have touched upon. So make sure you allocate a lot of time for debugging the circuit. The biggest problem I see is that you will HAVE to have hysteresis in the switchover, otherwise the output will swing back and forth between 0.1 and 0.01V.
simulate this circuit – Schematic created using CircuitLab
- \$\begingroup\$ Dear @mkeith But mux is binary, How will it so these low voltage lines at Output. Are u suggesting analog multiplexer...... \$\endgroup\$Raj Kiran– Raj Kiran2020-09-09 17:27:07 +00:00Commented Sep 9, 2020 at 17:27
- \$\begingroup\$ Yes. It must be an analog multiplexer. But I didn't see a symbol for an analog multiplexer so I used the digital one. \$\endgroup\$user57037– user570372020-09-09 17:37:07 +00:00Commented Sep 9, 2020 at 17:37
- \$\begingroup\$ I was thinking of two mosfets and a demux to select different outputs \$\endgroup\$Raj Kiran– Raj Kiran2020-09-09 17:44:04 +00:00Commented Sep 9, 2020 at 17:44
- \$\begingroup\$ Might work, but you may be able to reduce design/debug time by using an off-the-shelf analog switch. One thing to consider is capacitive coupling between input and output. This can reduce isolation of a single transistor switch at AC. Chip designers will take steps to improve this. You can too, but it adds complexity and discrete part count. \$\endgroup\$user57037– user570372020-09-09 18:04:18 +00:00Commented Sep 9, 2020 at 18:04
- \$\begingroup\$ Thank you for the support. \$\endgroup\$Raj Kiran– Raj Kiran2020-09-10 13:14:49 +00:00Commented Sep 10, 2020 at 13:14
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2 You can logically build that from comparators, and adders (both can be built using operational amplifiers), and voltage references. (That's enough hints; this clearly is homework.)
Notice that after building this, you'll notice how much of a terrible idea this is; if your voltage is somewhere between say 998 mV and 1002 mV and you have say a 10 mV RMS noise (which isn't really much), imagine how badly your output would be jumping! I doubt this specification has any practical use but to teach you basic opamp circuitry, and how to build a system from logical components like summers, comparators.
However, this is a trick question: You're building a device that has < 1 mV of accuracy. Not a trivial thing to do with standard components.
While selecting your opamps, you will have to take input offsets into account; when selecting voltage standards, you will have to pick ones that are accurate enough. So, you'd instantly fail if you're trying to do that with an xx741 opamp and an uncompensated zener!
Getting precision resistors and voltage references will be key here, and so will be designing your feedback such that variations don't add constructively.
- \$\begingroup\$ Dear sir any reference online links are appreciated. I tried on goggle but couldnt found. \$\endgroup\$Raj Kiran– Raj Kiran2020-09-08 17:06:32 +00:00Commented Sep 8, 2020 at 17:06
- \$\begingroup\$ that's not something you can google. You know basic opamp circuits, this is such a typical excercise for students that have learned these, so apply that knowledge. \$\endgroup\$Marcus Müller– Marcus Müller2020-09-08 17:06:43 +00:00Commented Sep 8, 2020 at 17:06