Timeline for How can I efficiently drive an LED?
Current License: CC BY-SA 4.0
11 events
| when toggle format | what | by | license | comment | |
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| S Jun 5, 2024 at 13:36 | history | suggested | Codebling | CC BY-SA 4.0 |
Replace broken link with archive.org
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| Jun 5, 2024 at 4:07 | review | Suggested edits | |||
| S Jun 5, 2024 at 13:36 | |||||
| Sep 2, 2017 at 8:23 | comment | added | andrea | Adding a resistor RS in series with the source (LED side) allows current regulation below the maximum available current I_DSS at VGS=0. Voltage drop across RS is made equal to -VGS and the circuit will find an equilibrium at a lower current: the larger RS the lower the current, until the desired one. | |
| May 26, 2017 at 18:28 | comment | added | rdtsc | Hence why I said "you can throw anything from about 4v to 20v at it". Of course power dissipation has to be taken into consideration, and ~20v is the max for this device. Efficient? Not really. But quite useful. If you can find a simpler way to drive an LED from 4v to 20v with a current of +/-0.3mA, we'd love to see it. | |
| Jan 20, 2017 at 17:36 | comment | added | dannyf | "There is one other way, much less commonly seen." The JFET forms a CCS, so conceptually it is not different from those approaches being discussed earlier. It is much less used for two reasons: 1) JFETs have very poor consistency from device to device; 2) the power dissipation on the JFET can easily exceed its rating. | |
| Apr 4, 2016 at 2:50 | comment | added | rdtsc | Although this is an unorthodox usage for a JFET, this effect can be explained by the "Zero–Gate–Voltage Drain Current" rating in the datasheet. With the gate tied directly to the source, the gate always appears as 0v, so the JFET behaves as though it is "on." The conduction channel inside the JFET is narrow enough that it effectively limits the amount of current that can flow through it. This phenomenon varies greatly with different JFETs and even devices from the same batch. (The 2N3819 is rated 2-20mA; 12mA is a typical value.) | |
| Feb 3, 2016 at 22:28 | comment | added | Yarek T | What witchcraft is this? How does this even work? | |
| S Apr 24, 2015 at 21:51 | history | edited | rdtsc | CC BY-SA 3.0 |
Fixed label.
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| S Apr 24, 2015 at 21:51 | history | suggested | Greg d'Eon | CC BY-SA 3.0 |
Fixed image
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| Apr 24, 2015 at 21:49 | review | Suggested edits | |||
| S Apr 24, 2015 at 21:51 | |||||
| Apr 24, 2015 at 21:45 | history | answered | rdtsc | CC BY-SA 3.0 |