current between collector and emitter

Thread Starter

WyleECoyote

Joined Jun 19, 2019
6
I'm finding that my s8050, BJT, NPN transistors are conducting current from Collector to Emitter ALSO.
I don't want to add Zenor diodes.
Is there a transistor out there... that TRULY conducts current JUST 1 way between Emitter and Collector????

Thanks,
 

BobTPH

Joined Jun 5, 2013
2,057
That is indeed the case, if reverse biased. Generally circuits are designed such that this will not happen. What are you trying to do?

Bob
 

Thread Starter

WyleECoyote

Joined Jun 19, 2019
6
That saves me unnecessary research along with trial and error.
So, I will have to use Zenor Diodes then.

My project is an array of LEDs, but current can apparently "backfeed" through other transistors in the array.

There are a lot of "official" posts out there about NPN vs PNP... and most fail to admit this.
I must be the 1,999th victim?

:mad::(
 

Thread Starter

WyleECoyote

Joined Jun 19, 2019
6
I'm not duplicating any proven circuit, so I know I'm experimenting.
I was providing 3.2+ at the Emitter and 3.2+ at the base.
I will check on the 'breakdown voltage' E<--->C for an S8050.
But I got to have 3.2 for these LEDs.
Thanks for all your help so far!!
 

crutschow

Joined Mar 14, 2008
23,533
A BJT will operate as a transistor when the emitter and collector are reversed, but with very low gain, and with the low breakdown voltage of the base-emitter junction (now collector-emitter).
 

djsfantasi

Joined Apr 11, 2010
5,704
Do you have a schematic?

What are you using as a 3.2V source? I’m concerned about the statement “I got to have 3.2 for these LEDs”!

Do you know that LEDs are current controlled devices and not voltage controlled? If you were to connect an LED with a 3.2V forward voltage directly to a 3.2V supply, do you expect it to work? I bet that it will fail.

Also, are you connecting 3.2V directly to the base? Again, expect failure.

I’m just guessing because you haven’t provided a schematic. But do you think it’s possible that your transistors are backfeeding because they’ve been compromised or destroyed?
 

Thread Starter

WyleECoyote

Joined Jun 19, 2019
6
Yet another thread where the TS is withholding the info necessary to solve the problem.

Bob
Yet another site/forum where the Senior Members make cynical remarks on new persons just trying to learn.

I'll spend an hour drawing the schematic, then I'll take it to another site.

Bye.
 
Yet another site/forum where the Senior Members make cynical remarks on new persons just trying to learn.

I'll spend an hour drawing the schematic, then I'll take it to another site.

Bye.
I would really like to help but the schematic is important. I'll also answer your original question; yes there are transistors that truly conduct one way, provided you don't exceed the limits on the specification. If we knew what the circuit looks like we may be able to tell if the limits are being exceeded and recommend a better transistor.
 

MrChips

Joined Oct 2, 2009
19,422
I'm finding that my s8050, BJT, NPN transistors are conducting current from Collector to Emitter ALSO.
I don't want to add Zenor diodes.
Is there a transistor out there... that TRULY conducts current JUST 1 way between Emitter and Collector????

Thanks,
I though an NPN transistor is supposed to conduct current from collector to emitter when properly biased.
 
I though an NPN transistor is supposed to conduct current from collector to emitter when properly biased.
That depends on if using conventional or electron current flow. It could be either way if you don't specify conditions.

I first learned electronics in the Navy. (electron current flow) but studied conventional current flow in college. So take your pick!
 

MrChips

Joined Oct 2, 2009
19,422
That depends on if using conventional or electron current flow. It could be either way if you don't specify conditions.

I first learned electronics in the Navy. (electron current flow) but studied conventional current flow in college. So take your pick!
Yes, I knew that. I was waiting for the TS to respond.
 
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