Timeline for Op-Amp nodal analysis
Current License: CC BY-SA 4.0
12 events
| when toggle format | what | by | license | comment | |
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| May 5, 2022 at 1:37 | comment | added | jonk | @samlikesham Glad that helped. :) It's not so complicated once you grasp a few things and keep them in mind. | |
| May 5, 2022 at 1:35 | comment | added | sam | @jonk Yes! Thank you, it makes sense now. | |
| May 5, 2022 at 1:24 | comment | added | jonk | @samlikesham Because the opamp OUTPUT is hooked backwards towards the (-) node and can PULL current. Nothing like that exists at the (+) input node. So it cannot happen. But it sure can happen at the (-) node. And the opamp will wiggle its OUTPUT in order to make sure that the (-) node is the same as the (+) node. Yes? | |
| May 5, 2022 at 1:19 | comment | added | sam | @jonk Yes, I meant the (+) input for Vin. So, because the current is zero, voltage potential at (+) input is Vb? Also, why is there current going through 20k resistor but not the 40k? | |
| May 5, 2022 at 1:16 | answer | added | Fred Cailloux | timeline score: 0 | |
| May 5, 2022 at 1:10 | comment | added | jonk | @samlikesham Where is Vin exactly? I'm not seeing it there. Or do you mean the voltage at the (+) input to the opamp?? If that is it, then yes, the voltage drop across the 40 k will be as you say. But... what's the current through the 40 k? Shouldn't it be zero amps? And therefore there is no drop across the 40 k resistor? | |
| May 5, 2022 at 1:03 | comment | added | sam | Wouldn't the voltage drop across the 40kOhm resistor be Vb - Vin+? | |
| May 5, 2022 at 0:25 | comment | added | D.A.S. | It might be misleading to see this i100 in the opposite direction of i20 because this is the inverting input and you assume no significant input current. So the output goes down with up in i20 so here i20= - i100 or if shown in the same direction are actually the same currents. But Vin+ is your null input reference so feedback forces Vin to follow Vin+=Vin- which are not 0V. | |
| May 5, 2022 at 0:04 | comment | added | John D | Ask yourself what's the voltage drop across the 40 kOhm resistor? What do you know about the voltage between the + and - terminals of an op-amp with high gain and negative feedback? | |
| May 5, 2022 at 0:03 | comment | added | jonk | Given what you see there, what voltage should appear at the (-) input node of the opamp? (This isn't a hard question.) | |
| S May 4, 2022 at 23:59 | review | First questions | |||
| May 5, 2022 at 4:52 | |||||
| S May 4, 2022 at 23:59 | history | asked | sam | CC BY-SA 4.0 |