Electronics > Beginners
MOSFETS as voltage controlled gates
SolderOcelot:
I need 3 gates in my circuit which each should close (as in: let current go through source and drain) IF the circuit voltage is > X.
My question: Are MOSFETS the right tool for this construction?
My goal is to create a LED strip that lights up a number of LEDS depending on voltage. Please take a look at attachment for schematic.
ArthurDent:
Here is an IC that is designed for this type of application and I'm sure there are some others.
https://www.ti.com/lit/ds/symlink/lm3914.pdf
SolderOcelot:
--- Quote from: ArthurDent on November 18, 2018, 12:34:37 am ---Here is an IC that is designed for this type of application and I'm sure there are some others.
https://www.ti.com/lit/ds/symlink/lm3914.pdf
--- End quote ---
On one hand I think it's pretty cool that IC's come onto my path now but on the other hand it's quite a buzzkill to just slap an iC on there and be done with the project. I was hoping to build this a bit more primitively.
Whales:
You could use varying amounts of diodes in series to each LED. The turn-on might not be as abrupt as you hope, however.
Another alternative is to use diode stacks that then feed the base of an NPN. That might have a sharper turn-on. I suspect FETs would again be too gradual of a turn on.
SolderOcelot:
--- Quote from: Whales on November 18, 2018, 01:33:50 am ---You could use varying amounts of diodes in series to each LED. The turn-on might not be as abrupt as you hope, however.
--- End quote ---
What do you mean with "abrupt"? As in speed in which LEDs switch on or the contrast between the LEDs' on and off state (diffusion).
--- Quote from: Whales on November 18, 2018, 01:33:50 am ---Another alternative is to use diode stacks that then feed the base of an NPN. That might have a sharper turn-on. I suspect FETs would again be too gradual of a turn on.
--- End quote ---
So with "diode stacks" the diodes act as voltage barriers right? So the first stack would require a voltage of 1.3 for current to go through right? If so, I'm worried about the amount of resistence they add to the circuit which would interfere with other features.
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