Timeline for Can I model a diode with higher than usual junction voltage in LTspice using the "Eg" and "Vj" parameters?
Current License: CC BY-SA 4.0
14 events
| when toggle format | what | by | license | comment | |
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| Feb 4, 2023 at 10:05 | vote | accept | tobalt | ||
| Feb 4, 2023 at 10:01 | answer | added | Ste Kulov | timeline score: 3 | |
| Feb 4, 2023 at 9:00 | history | tweeted | twitter.com/StackElectronix/status/1621795712928284672 | ||
| Feb 4, 2023 at 8:50 | comment | added | tobalt |
@SteKulov The simple model works well indeed, but is not available as body diode in VDMOS afaik. N and resistance affect the MOS channel too, though its effects could be compensated. You could transform your comment as an answer, because it explains my sim question completely. Thanks.
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| Feb 4, 2023 at 7:59 | comment | added | Tim Williams | If you're modeling the MOS, you already have this: there is no body diode on these devices, it's simply the Vgs curve for D/S swapped and Vgs = 0. That is, it should have a quadratic not exponential asymptotic shape, which a SPICE diode won't fit well. (To say nothing of tempco, but alas I'm very unfamiliar with all the MOS parameters in SPICE.) | |
| Feb 4, 2023 at 7:59 | comment | added | Ste Kulov |
Correct. Eg only effects temperature dependence (not just on Is, but on Vj too). However, Vj itself only affects the nonlinear junction capacitance. If you want to change the static DC characteristics, you need to adjust Is, N, and Rs (as already mentioned). If you want more direct control over the forward voltage, it might be better to use LTspice's alternate piecewise-linear diode model along with the epsilon parameter. A great answer for working with the standard model can be found here: electronics.stackexchange.com/a/9543
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| Feb 4, 2023 at 4:51 | comment | added | periblepsis | I remember that Eg does affect the temperature dependence of ISAT. So, try to adjust the operating temperature to see if your value of Eg does show up as a change in the V-I curve at different temperatures. | |
| Feb 4, 2023 at 4:05 | history | edited | tobalt | CC BY-SA 4.0 |
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| Feb 4, 2023 at 3:59 | comment | added | tobalt |
@periblepsis Yes. These all have the expected influence on the behavior, when I change them..So I surely could create the desired behavior with them alone. Or even just with a voltage dependent resistor... Still I am wondering why the Eg and Vj settings have no effect, because I guess they were intended for changing the diode material.
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| Feb 3, 2023 at 18:51 | comment | added | periblepsis | Have you considered that N and ISAT (and the series bulk impedance RS) all impact the forward voltage? | |
| Feb 3, 2023 at 9:41 | history | edited | tobalt | CC BY-SA 4.0 |
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| Feb 3, 2023 at 8:42 | history | edited | JRE | CC BY-SA 4.0 |
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| Feb 3, 2023 at 8:37 | history | edited | winny | CC BY-SA 4.0 |
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| Feb 3, 2023 at 8:32 | history | asked | tobalt | CC BY-SA 4.0 |