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I make a small solar energy harvester. I'm searching for the type of diode with lowest drop voltage. Any suggestion for the type of diode for me ?

Thank you

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    \$\begingroup\$ If you study diodes, they don't have a threshold voltage as such but sometimes it's convenient to refer to a value between 0.5 volts and 1 volt. Try looking for schottky diodes as they have the lowest forward volt drop for a given current. Germanium diodes are also worth looking at but their availability and reliability is somewhat degraded. \$\endgroup\$ – Andy aka May 22 '19 at 10:50
  • \$\begingroup\$ Thanks for your answer, i used 1N4148 diode, may be any diode better than 1N4148 \$\endgroup\$ – Back Link May 22 '19 at 10:54
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    \$\begingroup\$ How exactly do you intend to use them? \$\endgroup\$ – Lundin May 22 '19 at 11:12
  • \$\begingroup\$ @Lundin i use two diodes, one on the output of solar cell, one on the output of boost converter \$\endgroup\$ – Back Link May 22 '19 at 11:23
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    \$\begingroup\$ In series with the supply? Then you definitely need a different diode. There's specialized fast diodes suitable for use together with regulators, for example. I would advise you to post a simple schematic on this site (there's a free schematic tool you can use) and ask for feedback about component choice. \$\endgroup\$ – Lundin May 22 '19 at 11:26
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Most diodes will be better than 1N4148. Diodes for higher current will usually have less voltage drop at lower current. As Andy says, Schottky diodes will have lowest voltage drop. At about 200 mA voltage drops for common diodes are (from various datasheets):

DIODE     Vdrop @ 200 mA    Diode type
1N4148    1.0               Signal
1N4007    0.8               General rectifier (1A)
1N5408    0.6               General rectifier (3A)
1N5817    0.25              Schottky (1A)
1N5820    0.2               Schottky (3A)
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  • \$\begingroup\$ Recently I measure the 1N4148 on my circuit at anode and cathode, the avometer show 0.16v, would you like to explain to me about that?, i'm newbie in electrical, Thank you \$\endgroup\$ – Back Link May 22 '19 at 11:29
  • \$\begingroup\$ @BackLink en.wikipedia.org/wiki/Diode_modelling#Graphical_solution \$\endgroup\$ – Sean Houlihane May 22 '19 at 12:15
  • \$\begingroup\$ @SeanHoulihane understand this. On a Log I vs linear V diodes are a straight slope until bulk Rs takes over then on a Linear I vs V it is a straight slope . Aka stepwise approximation aka linear regression, so some Schottky diodes reach the same as silicon or more when higher than rated using pulsed currents. \$\endgroup\$ – Tony Stewart EE75 May 22 '19 at 13:20
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    \$\begingroup\$ @BackLink What was the current flow through the diode? At negligible current flow, you can get very low voltage drop across the diode. This is why it is not always a good idea to power sleeping chips through diodes. If current draw reaches uA levels, the voltage supplied to the chip may exceed specifications. One cannot blindly use 0.7 V as diode drop. Check the datasheet to see the minimum current specified on the charts. \$\endgroup\$ – Indraneel May 22 '19 at 16:41
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You can try something like the 1N5817 Schottky diode, but note that lower drop goes hand-in-glove with higher reverse leakage (particularly egregious at higher temperatures).

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  • \$\begingroup\$ @SpehroThanks for your suggestion \$\endgroup\$ – Back Link May 22 '19 at 11:24
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For harvesting low voltage, you might want to consider the ideal diode using 1 FET , 2R’s and an IC or buy the board online.

Understanding an 'ideal' diode made from a p-channel MOSFET and PNP transistors

Or if the cost justifies a better solution, this energy harvesting IC BQ25505 which specs include :
– Ultra-Low Quiescent Current of 325 nA.
– Input Voltage Regulation Prevents Collapsing High-Impedance Input Sources

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Firstly you should post a quick schematic of what you're working with. Schottky diodes are the kind with the lowest voltage drop. But your common models will still drop around 200mV.

There are ways to achieve the same result as using a diode, without the voltage drop. But it's more complicated and would depend on your design.

For solar energy harvesting though, you should be fine with a single Schottky between your panel and the rest of your design. Something like a 30V/3A would work with your average panel and have a pretty low voltage drop. Of course that all depends on what panel(s) you are using and what is connected to them...

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    \$\begingroup\$ "Schottky diodes ... common models will still drop around 2mV." - Did you mean 200mV? \$\endgroup\$ – marcelm May 22 '19 at 15:12
  • \$\begingroup\$ Yes, sorry 200mV \$\endgroup\$ – hekete May 23 '19 at 3:00
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If you are just using the diodes to mux two power sources then you can use an ideal diode chip.

https://www.analog.com/en/parametricsearch/11029

They typically consume micro-amps of current. The forward voltage drop is usually only a few mV.

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