Author Topic: Need help identifying transistor symbols  (Read 3501 times)

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Offline chipwitchTopic starter

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Need help identifying transistor symbols
« on: April 17, 2013, 05:51:14 pm »
I'm sure someone here knows what these are...

Plus, one between the two circles?  Is it just a bjt?  The wire piercing the base looks like it could be a fourth terminal.

Thank you
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Online madires

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Re: Need help identifying transistor symbols
« Reply #1 on: April 17, 2013, 06:01:37 pm »
Top down:
- PNP BJT with dual collector
- NPN BJT with a connection to the base crossing the BJT symbol :-)
- NPN BJT with dual emitter
« Last Edit: April 17, 2013, 06:04:45 pm by madires »
 

Offline chipwitchTopic starter

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Re: Need help identifying transistor symbols
« Reply #2 on: April 17, 2013, 06:06:20 pm »
I just knew I'd get a fast answer here! ;)

Thanks for the response.  I'd never heard of dual terminals before.... something new to learn :)
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Online PA0PBZ

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Re: Need help identifying transistor symbols
« Reply #3 on: April 17, 2013, 06:10:56 pm »
You see these a lot in digital logic, for instance this is how you make a NAND gate:

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Offline chipwitchTopic starter

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Re: Need help identifying transistor symbols
« Reply #4 on: April 17, 2013, 07:48:47 pm »
Okay... so the two emitter connections act as the two inputs and the path to the right, between q1 and R2 is the output?  Either emitter is able to conduct through the collector?  The same would be true for the double base transistor as well then?
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Online PA0PBZ

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Re: Need help identifying transistor symbols
« Reply #5 on: April 17, 2013, 07:58:44 pm »
I'm not sure if it is a double base or just a convenient/weird way of drawing a connection.
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Online madires

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Re: Need help identifying transistor symbols
« Reply #6 on: April 17, 2013, 08:10:20 pm »
I'm not sure if it is a double base or just a convenient/weird way of drawing a connection.

I'd go for the latter, because a (second) base should be drawn opposite of emitter and collector.
 

Offline chipwitchTopic starter

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Re: Need help identifying transistor symbols
« Reply #7 on: April 17, 2013, 08:23:47 pm »
I found something called a lateral bipolar that has a symbol bisecting the emitter and collector.  Could that be it?
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Online madires

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Re: Need help identifying transistor symbols
« Reply #8 on: April 17, 2013, 08:39:38 pm »
I found something called a lateral bipolar that has a symbol bisecting the emitter and collector.  Could that be it?

AFAIK, lateral specifies the way the transistor is built. The other one is vertical.
 

Offline MacAttak

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Re: Need help identifying transistor symbols
« Reply #9 on: April 17, 2013, 10:46:53 pm »
Both of the symbols are described on this page: http://www.allaboutcircuits.com/vol_3/chpt_4/14.html (scroll to the bottom)

As mentioned already, the middle transistor symbol is just a convenient way to lay out the schematic.

The top and bottom transistors have double emitter or double collector. In essence, this just means a transistor with a larger die area (to carry higher current). It is basically the same thing as having two transistors with base plus collector (or base plus emitter) wired together. But normally this would mean slight temperature differences between the two - and this would cause them to behave ever so slightly differently. So they are packed close together on the same substrate, thereby keeping any thermal differences at an absolute minimum.
 


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