Timeline for Error in constant current sink circuit and current regulator
Current License: CC BY-SA 4.0
8 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jan 11, 2021 at 8:32 | comment | added | user57037 | One thing that is interesting is that the diodes may compensate for Vbe's temperature coefficient somewhat. Or I guess you could say it the other way around, that Vbe's temperature coefficient compensates for the fact that that the diode reference varies with temperature. Ironically using a good voltage reference for the base may make the temperature performance worse. Or maybe not since the diode tempco is double, and also different from the transistor. | |
| Jan 11, 2021 at 4:05 | comment | added | Pete W | sorry, when I wrote that I missed the fact that the point of this was a constant 12V, i.e. constant current into the diodes. | |
| Jan 11, 2021 at 0:37 | comment | added | Bruce Abbott | @PeteW Temperature effects were not simulated! Let's not get too pedantic... (and the diodes only pass 11mA with their 12V supply. LTspice says 7.4mW per diode, which corresponds to ~2ºC temperature rise). | |
| Jan 11, 2021 at 0:11 | comment | added | Bruce Abbott | "And isn't an ideal diode a voltage regulator" - depends on your definition of 'ideal'. Mine is a diode with no forward voltage drop at all. Another definition (which I believe LTspice uses) is one that perfectly follows the Shockley diode equation which is not much different to a real diode. I always use real components in simulations whenever practicable, because 'ideal' or generic parts can give misleading results (perhaps even leading to designing something that cannot exist in the real world!). | |
| Jan 10, 2021 at 22:03 | comment | added | jonk | @CloneWars No. The ideal diode will just make sure that the voltage across the load is constant, if in parallel. If the load varies, its current will vary. Which is not a constant current. Assuming I'm following you, anyway. | |
| Jan 10, 2021 at 21:17 | comment | added | Clone Wars | And isn't an ideal diode a voltage regulator(if it is connected in parallel to the load)? | |
| Jan 10, 2021 at 21:15 | comment | added | Clone Wars | Bruce if I change the collector voltage , the collector current doesn't change if I remember correctly just the Vce(Collector-Emitter) voltage is changed . | |
| Jan 10, 2021 at 20:36 | history | answered | Bruce Abbott | CC BY-SA 4.0 |