The Zeptobars Explain This Transistor To Me Challange

[JoeN]

First, check out the latest microscope image Zeptobars came up with:

http://zeptobars.ru/en/read/BFG135-NPN-7GHz-RF-BJT

Now, there are three terminals here.  Let's call them left, middle, right.  Middle and right seem to be connected.  So what terminals are what?  My wild guess is left is emitter and middle is base.  Is that right?  If so, right is base too - and it doesn't look like anything was soldered there anyway.  So the collector is tied to the substrate?  And why two bases?  Is it so that two different devices with different base characteristics can be made from one die - just bond the wire to a different pad?

Anyway, it's interesting to me.  I don't know anything about semiconductor fabrication.  Tell me what is going on here if you do and are to take the time.  Zeotobars never explains what is going on, even on three terminal devices where I think it is probably possible to give an explanation.

[rs20]

7GHz RF NPN transistor with integrated emitter-ballasting resistors. Transistor is so sparse to lower thermal (mainly) and collector resistance.

So, we know that there are resistors on the emitter, and the thicker wire in the middle tells me that's the emitter. The comment about tells us that the parts are spread out to minimize collector resistance; which tells us that the collector is the substrate. I guess the two pads on the emitter are to allow two bond wires for reduced lead resistance? And the left is the base by deduction.