Timeline for How to determine the correct polarity of the diode
Current License: CC BY-SA 4.0
7 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Feb 24, 2019 at 20:43 | comment | added | DKNguyen | Perhaps your confusion is somewhat rooted in the transformer +/- labellings of your first picture. No input signal is shown so you have no idea what the polarities actually are. Thus, the +/- are just relative labels. If you apply a voltage/current to the transformer such that positive goes to the + label negative to the - label, then you will get + polarity everywhere it says + and - polarity everywhere it says -. If you apply the opposite, you get the opposite. You could replace all the +/- labels with A/B labels and it would be the same. They are relative labels. | |
| Feb 24, 2019 at 20:39 | comment | added | DKNguyen | You need to be very careful in your language here since you are dealing with an AC input. The 12V battery biases the entire AC input waveform by moving the graph up by 12V. So you have a net of 42V being applied in the first half cycle, and -18V being applied in the second half cycle. So in the first half cycle, positive cathode/negative anode. In the second half cycle, negative cathode/positive anode. | |
| Feb 24, 2019 at 20:30 | comment | added | khaled014z | Its highlighted now, the bottom right one, the problem that I'm having is when applying KVL, I seem to get some sign wrong and end up with a false output voltage | |
| Feb 24, 2019 at 20:28 | comment | added | DKNguyen | By "last circuit", you mean bottom right? | |
| Feb 24, 2019 at 20:26 | comment | added | khaled014z | Yes I only care about the potential difference applied on the diode, since D3's cathode is positive by the top terminal of the transformer, can I use the same logic and apply it to the last circuit in the second picture and say that the cathode of the diode is positive with respect to the anode? | |
| Feb 24, 2019 at 20:23 | comment | added | DKNguyen | Just repeating this again for emphasis: "The diode polarities in that drawing are the actual voltages applied to the diodes, not some innate properties of the diode." Anode and cathode are terminals on the the diode. If you make the anode positive and the cathode positive it will behave a certain way, if you reverse the polarity it will behave another way. Diodes that are meant to do their job by conducting current (most diodes, LEDs, schotky) will do so with a positive anode/negative cathode. Diodes whose job is to clamp voltage (zener, TVS) do their job with negative anode/positive cathode. | |
| Feb 24, 2019 at 20:19 | history | answered | Peter Bennett | CC BY-SA 4.0 |