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brodin said:I need a diode that has a constant voltage drop at either 0.9 or 1.0 v. What diode should i use?
brodin said:It is for the circuit you helped me with, the current limiting circuit. The voltagedrop over the diode/diodes are critical. I cant use 2 1N4148 (0.7v each). Then the output current gets to low under 12V input.
But if i have a lower voltage drop, say 1V and a lower resistance value, then 12V works fine.
So it don't have to be constant, but it have to be rather close to 1V to work fine.
Someone said to me that a 1N4001 had a 1V drop. Would that diode work?
You could always split your LED's into two chains, and have two transistors and two 22 ohm resistors - you can connect the two bases together, and use the same pair of diodes and feed resistor to set both base voltages.
brodin said:You could always split your LED's into two chains, and have two transistors and two 22 ohm resistors - you can connect the two bases together, and use the same pair of diodes and feed resistor to set both base voltages.
Well the led's are in a module(6 leds), with only 2 pins out, Anode and Cathode. So splitting up isn't an option.
Oznog said:Hmm... constant 1v?
Well, you can't use a zener because the lowest voltage used with Zeners is 1.8v.
You could put a normal rectifier diode in series with a Schottkey. Normal rectifier is 0.7v and Schottkey is 0.3v. The voltage will rise a bit as current rises though, it is not extremely tightly controlled. Temp changes it a small amount too.
But you mention LEDs? So I assume you're doing that common emitter circuit. For this, so you see the tricky problem in these. You need either a really specific driving voltage or a really specific low ohm resistor.
FRIED said:Try
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