How are close loops with resistors biased in this bipolar analog IC?

Status
Not open for further replies.
X

xihuwang

Member level 2
Joined
Oct 23, 2007
Messages
46
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,288
Activity points
1,595
Hi,everyone :
Need your help !
I am analysis an bipolar analog IC's picture . There are many resistor (
they are base diffussion resistor I guess) in one island . The resistor are divided by
diffusion protection closed loops . I mean every resistor is in one closed loops, and
all resistors are in one island . But I can't find how these loops are biased . I mean
these loops are float and not connect to vss or vdd.
So , any body can teach me , what is the problem or what is the structure
of this bipolar process.


Thanks forwads !

Ohh, additionally, I can't find the vdd pad !
 

bipolar analog IC

The resistors are normally in an N well which needs to be biased to the most positive voltage on the chip.

What process are you using?

Keith.
 

Re: bipolar analog IC

It is bipolar process with P-sub , n-epi. There is no well .
Yes , the base-diffusion resistors are protected by closed protection loop. What
puzzle me is that the loops seem to be float , I can't see they are connected
with vdd or gnd !

Added after 1 minutes:

What makes me surprise more is that a npn transistor's collecter
is connected with the loop.
 

bipolar analog IC

Could you say the process - manufacturer & process name? It will be a lot easier to comment then. The epitaxial layer will be N type and forms the well wit the base resistors in it, isolated by isolation diffusion would be my guess.

Keith.
 

bipolar analog IC

It might be that the resistor bank is subject to a reversing
voltage, and the only option was to let the isolation float to
the highest / lowest potential (dragged by diode). A hard tie
would make the resistor asymmetric electrically.
 

Re: bipolar analog IC

But some transistor's collector is connected with the base resistor's protection closed loop. Can transistor's collector be floated ?

Added after 11 minutes:

When I say base resistor, it means the resistor type that is made up of a strip of base diffusion. I think the n-tank connected usually to power.But why the n+ loop
around the base resistor is float (so the n-tank is also float)?
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…