Two different bipolar transistor symbols - what's the difference?

[c4757p]

(No, not NPN vs PNP )

I've seen this a few times, and haven't been able to figure it out. In this datasheet and others, in the schematic, there are two different transistor symbols: one with a line for the base (e.g. Q1 on the far left), and one with an outlined rectangle (e.g. Q5 just above it). What's the difference?

[Wytnucls]

Darlington pair, perhaps?

[Tube_Dude]

A normal PNP transistor, just with collector shorted to base, to behave like a diode...

[IanB]

I guess to clarify, this:



vs this?



I don't have a clue either.

[Tube_Dude]

I guess to clarify, this:

The one at the right in the pic...

( this one is a NPN )

[Shuggsy]

I guess to clarify, this:

The one at the right in the pic...

( this one is a NPN )

Doesn't seem to make sense with the transistor pairs in the schematic c4757p linked to in the first post. Pairs like Q3/Q4, Q5/Q6, and Q15/Q17. Why have diode pairs like that? Then there's the question of why they marked some transistors like that and others with the base explicitly tied to the collector (Q7, Q22, Q27... Q27 even has the different schematic symbol already!). Very interesting.

Maybe those require a larger Vbe to turn on? Some kind of insulated base or different doping concentrations?

[IanB]

The one at the right in the pic...

No, not that. I clarified c4757p's question to make the specific symbols clear. The original question was about the symbol used for Q1 (or Q2) vs the symbol used for Q5 (or Q6). The difference is that for one transistor the substrate is drawn as a single line, whereas in the other it is drawn as a hollow rectangle. What is the significance of drawing the transistor with a hollow rectangle like that?

To emphasize again, what is the significance of drawing a transistor with this symbol?

[Tube_Dude]

I see! I have misunderstood the original question. 

Oh, my English!! 

[amyk]

My guess is a thicker base region.

You can ask Linear about it, I think they were the ones who came up with that schematic.

[Simon]

could it just be that they are using two main types of transistors and that is their way of differentiating them, it's an internal code

[alanb]

could it be the diffrence between germanium and silicon?

[Tube_Dude]

could it be the diffrence between germanium and silicon?

Don't think so. Germanium in an integrated circuit substrate...

[c4757p]

IanB is right, I was asking about the difference between those two symbols, not diode-connected transistors.

[Gall]

could it be the diffrence between germanium and silicon?

No. Both are silicon.

Looks like just two different IC mask layouts, i.e. a "small transistor" and "large transistor".

[Arion02]

Could it be an Isolated Gate Bipolar Transistor (IGBT)?



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[T4P]

Might mean some amount of capacitance 

[Simon]

like a more powerful transistor

[AlfBaz]

As far as I can see they're in pairs, more specifically "long tail" pairs. The symbol probably represents matched pairs