Author Topic: Transistor electrical characteristic  (Read 1064 times)

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Offline Jane

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Transistor electrical characteristic
« on: July 26, 2016, 06:35:09 pm »
I checked a datasheet of a transistor and there are few characteristics I do not understand

Collector-base breakdown voltage
Collector-emitter breakdown voltage
Emitter-base breakdown voltage
Collector cut-off current ICBO
Collector cut-off current ICEO
Emitter cut-off current IEBO

Can anyone please explain these voltages given above?

Is Emitter-base breakdown voltage  a minimal voltage that  transistor needs to start working?
 

Offline Kilrah

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Re: Transistor electrical characteristic
« Reply #1 on: July 26, 2016, 06:45:44 pm »
Breakdown voltage is the voltage at which something will start conducting even when it's not supposed to. A transistor is never supposed to let current flow between collector and base, but if you exceeded the collector-base breakdown voltage it couldn't hold it anymore.
 

Offline Refrigerator

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Re: Transistor electrical characteristic
« Reply #2 on: July 26, 2016, 07:03:35 pm »
Collector-base breakdown voltage
- Maximum voltage that can be between collector and base without damaging the transistor.

Collector-emitter breakdown voltage
- Maximum voltage that can be between collector and emitter without damaging the transistor.

Emitter-base breakdown voltage
- Maximum voltage that can be between emitter and base without damaging the transistor.

Collector cut-off current ICBO
Collector cut-off current ICEO
- ( from google ) "Collector cutoff current is the IC that still flows when the specified VC and a specified reverse bias is applied. It is normally less than either ICEO or ICER (collector current with the base open, or with the base resistively connected to the emitter)."

Emitter cut-off current IEBO
- ( from google ) "emitter cutoff current, collector open (IEBO)

The dc current into the emitter terminal when it is biased in the reverse direction with respect to the base terminal and the collector terminal is open-circuited. (Ref. IEEE Std 255.)"
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Offline PA4TIM

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Re: Transistor electrical characteristic
« Reply #3 on: July 26, 2016, 07:41:17 pm »
Download this book from tektronix. It is from the concepts series. It is about measuring semiconductors with a curvetracer but to do that you need to know all those parameters so they explain them all
http://w140.com/tekwiki/images/a/a0/062-1009-00.pdf

There is a whole range of books in this series from the 60's and many of them are still very usable.
http://w140.com/tekwiki/wiki/Concepts_Series

And to add something often is misunderstood, hFE is not the same as hfe
(for most it is written with a h and not a H) FE in capitals is the DC gain, fe is a bit more complex but in a nutshell you can see it as the small signal gain. The datasheet always states the hFE and sometimes hfe
« Last Edit: July 26, 2016, 07:51:57 pm by PA4TIM »
www.pa4tim.nl my collection measurement gear and experiments Also lots of info about network analyse
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http://www.youtube.com/user/pa4tim my youtube channel
 
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Offline Audioguru

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Re: Transistor electrical characteristic
« Reply #4 on: July 26, 2016, 10:42:23 pm »
Did you notice that the datasheet said, "emitter-base breakdown voltage" but did not say base-emitter breakdown voltage? That is because a transistor base-emitter normally has a forward bias voltage and it limits its own voltage to about 0.7V. The heating is low. If the emitter-base has a reverse bias voltage of about 5V or more then it suddenly has avalanche breakdown and conducts as much current as it can like a zener diode and it becomes too hot causing damage.
 

Offline madires

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Re: Transistor electrical characteristic
« Reply #5 on: July 26, 2016, 11:03:13 pm »
Collector cut-off current ICBO
Collector cut-off current ICEO
- ( from google ) "Collector cutoff current is the IC that still flows when the specified VC and a specified reverse bias is applied. It is normally less than either ICEO or ICER (collector current with the base open, or with the base resistively connected to the emitter)."

Emitter cut-off current IEBO
- ( from google ) "emitter cutoff current, collector open (IEBO)

Complicated names for leakage current :) It's very simple. The first two letters are the pins for which the leakage current is given, and the 'O' means the third pin is "open". Also the voltage applied to the pins is stated, like V_CE for I_CEO. I_CES is similar, but with the base shorted to the emitter, hence the 'S'.
 


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