Timeline for Trouble understanding when voltages get split
Current License: CC BY-SA 4.0
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| Apr 16, 2020 at 18:04 | comment | added | jonk | @lm1998 Also, keep in mind that your opamp doesn't have a reference to ground unless you provide one. It has access to the "most positive" and "most negative" voltages you give it. It doesn't actually mysteriously know anything about where the circuit "ground" is at. Besides, that's a fictional idea we use to aid communication. You could just as well call the negative voltage "ground" and then show the positive voltage to the opamp as the difference value. Voltages are all relative -- they require two points, not one point. When "ground" is selected it helps ease communication. That's all. | |
| Apr 16, 2020 at 18:01 | comment | added | jonk | @lm1998 I actually thought that would be the easier part for you. Take a close look at your schematic (or my version of it.) You can reasonably assume that the V+ input to the opamp doesn't sink or source current (it's "high impedance" and doesn't "load" the two resistors at their joined node.) Therefore, all you have is two resistors sitting between a voltage and ground. This is exactly a resistor divider and it's taught in chapter 1 of any book on beginning electronics. What other voltage would you imagine there? | |
| Apr 16, 2020 at 16:30 | comment | added | lm1998 | I guess what confuses me most is why the calc for V(+) is a voltage divider. Is it because we're only interested in what the voltage is from ground? | |
| Apr 16, 2020 at 13:29 | history | edited | jonk | CC BY-SA 4.0 | deleted 29 characters in body |
| Apr 16, 2020 at 13:29 | comment | added | jonk | @ElliotAlderson I'll remove the unnecessary comment. | |
| Apr 16, 2020 at 6:15 | history | edited | jonk | CC BY-SA 4.0 | added 161 characters in body |
| Apr 16, 2020 at 5:25 | history | answered | jonk | CC BY-SA 4.0 |