NPN and PNP Transistor configuration puzzling me

Thread Starter

chin kee ming

Joined Aug 3, 2019
3
Hai I am a beginner hobbyist tried to do transistors configuration but i met some questions i really don't understand
I have attached two pictures that i did for my transistor configuration but are that possible with that case

a) the NPN Transistor, I don't have to bias the Base and I can turn on the LED :confused:
b) PNP Transistor, I don't need the collector connection, I can turn on the LED:oops::oops:

Can everyone explain to me why these could happen???

Isn't that those transistors are malfunction? I had tried a whole batch of the Transistors (NPN & PNP) but all showed the same result:confused::confused::confused:
 

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danadak

Joined Mar 10, 2018
4,057
a) Transistor leakage and enough beta will procude enough current to
turn LED partially on. Many LEDs now with uA thru them can put out enough
light to be visible.

b) Basically you have BE junction acting as a diode forward biased, so again
current will flow thru LED.


Regards, Dana.
 

Thread Starter

chin kee ming

Joined Aug 3, 2019
3
a) Transistor leakage and enough beta will procude enough current to
turn LED partially on. Many LEDs now with uA thru them can put out enough
light to be visible.

b) Basically you have BE junction acting as a diode forward biased, so again
current will flow thru LED.


Regards, Dana.
Thank you very much to you
 

Thread Starter

chin kee ming

Joined Aug 3, 2019
3
a) Transistor leakage and enough beta will procude enough current to
turn LED partially on. Many LEDs now with uA thru them can put out enough
light to be visible.

b) Basically you have BE junction acting as a diode forward biased, so again
current will flow thru LED.


Regards, Dana.
Sorry to problem and asking the naive question
b) Basically you have BE junction acting as a diode forward biased, so again
current will flow thru LED.
if a PNP transistor's BE junction can act as a diode forward biased, so in what case the collector will come into play in PNP configuration
otherwise, I see that the collector will have no used at all
 

Audioguru

Joined Dec 20, 2007
11,249
No schematic and no transistor part numbers. The schematic or the datasheet for the part numbers will tell us which pins on the transistor are emitter, base and collector.

The basics of a transistor is that a small base-emitter current can cause a much higher collector-emitter current. Then you have a switch or an amplifier.
 

BobaMosfet

Joined Jul 1, 2009
1,878
Hai I am a beginner hobbyist tried to do transistors configuration but i met some questions i really don't understand
I have attached two pictures that i did for my transistor configuration but are that possible with that case

a) the NPN Transistor, I don't have to bias the Base and I can turn on the LED :confused:
b) PNP Transistor, I don't need the collector connection, I can turn on the LED:oops::oops:

Can everyone explain to me why these could happen???

Isn't that those transistors are malfunction? I had tried a whole batch of the Transistors (NPN & PNP) but all showed the same result:confused::confused::confused:
Title: Understanding Basic Electronics, 1st Ed.
Publisher: The American Radio Relay League
ISBN: 0-87259-398-3
 

SamR

Joined Mar 19, 2019
3,531
There IS a very clearly stated warning if you reply that states the age of the old post. So they ignored the warning! Go and try to reply to an old thread and see what happens. It's pretty darn obvious...
 

wayneh

Joined Sep 9, 2010
17,153
I'm not "blaming" anyone.
Just trying to understand what motivates them to do that.
I think it's a misunderstanding of the fluid nature of the forum. If you, as a new visitor, expect the knowledge here to be arranged by topic with each topic being added to incrementally, then a gap in time is to be expected. Instead, this place is a bit like a party, or a convention, with a bunch of different conversations all going on at once. In that model, going back to an old conversation is jarring. We get used to it but it's annoying to a beginner. It's so much harder to find anything.
 

AnalogKid

Joined Aug 1, 2013
9,378
Just trying to understand what motivates them to do that.
Not sure there is any specific motivation, like "Hey, here's a question with no activity for xx months; I think I'll jump right in." More like not noticing the posting dates when responding. Two days ago on another forum I saw a question about reducing the complexity of a small logic circuit that controls an electric train. I dipped in and out throughout the day with ideas, and eventually came up with a pretty good solution; all of the necessary functions with way fewer parts (28 soldered pins, down from over 60, one semiconductor type down from four). THEN I saw that the thread was 2 years old. Oh well ...

No, that site did not put up a warning about the age of the thread. Whatever, still a good circuit.

ak
 
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