Transistor Not Gate.

Discussion in 'General Electronics Chat' started by cjdelphi, Mar 26, 2009.

1. cjdelphi Thread Starter New Member

Mar 26, 2009
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http://www.kpsec.freeuk.com/trancirc.htm

at the bottom you have a simple NOT gate using a Transistor, the trigger which is fed to base goes through a 10k resistor is this used to limit the current from the short? I've built it and it works but i'm not totally sure how it works but here's how i /think/ it works.

The trigger, goes to base, the + (positive) to the collector and the - (negative) to the emitter, not for any other reason other than to supply the (let's for argument sake an LED) as the Base voltage saturates the transistor, the current flows from Collector to Emitter (Short???).. but to me this would mean a short, so does that mean the 10k resistor or the 1k deal with the short? or am i missing something?... what happens for the duration of the short which resistor does what?

http://www.kpsec.freeuk.com/images/trinvert.gif

2. thatoneguy AAC Fanatic!

Feb 19, 2009
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When the transistor is on, the collector is connected to 0V, the current through the transistor is limited by RC. The Current through the base-emitter junction is limited by RB

When the transistor is off, no current flows through the transistor, so no voltage is dropped across RC, So the collector is at the supply voltage.

Summary: When base is high, collector is low. When base is low, collector is high.

3. PRS Well-Known Member

Aug 24, 2008
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I believe this is just a switch that inverts the input at the output. It is therefore, logically speaking, an inverter, not a NOT gate. A gate has two or more inputs.

4. Ron H AAC Fanatic!

Apr 14, 2005
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Last edited: Mar 26, 2009

Jul 17, 2007
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6. Ron H AAC Fanatic!

Apr 14, 2005
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Thanks, SgtWookie. I almost always test my links. This is an example of Murphy's law.
How did you fix the link?

7. SgtWookie Expert

Jul 17, 2007
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Murphy was (and still is) a sonamabeesh!
I tried the copy/paste URL post like you used, and I got the same results with the forum's "auto URL tag" routine. It's definitely a forum software bug; I reported it in the "feedback" forum.

8. PRS Well-Known Member

Aug 24, 2008
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I thank you guys, too, for wising me up to the definition. It's been a while!