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current collapse - RF Cafe Forums
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satish.1979
Post subject: current collapse Posted: Thu Oct 05, 2006
3:30 am
Captain
Joined: Tue Oct 03, 2006 3:03 am
Posts:
11
Location: India
what is current collapse phenomena in tqhbt?
How can we overcome from that?
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Stephen
Post
subject: Posted: Tue Oct 10, 2006 2:56 pm
Captain
Joined:
Wed Jun 21, 2006 8:33 pm
Posts: 21
Location: Queen Creek, Arizona
satish,
"Current collapse" of heterjunction bipolar transistors
is an unwanted phenomena where, as a result of temperature extremes,
current becomes unevenly distributed across different legs of a device
(usually a single leg of a multi finger device experiences second order
effects such as thermal runaway). When this happens, the total current
gain of the transistor degrades and the collector current decreases,
causing the "current collapse".
There are several ways to
avoid it, some not as useful as others:
1. use a single legged
HBT (not useful, as it can still experience problems)
2. layout is
a key: proper layout can help with even temperature gradients across
the device.
3. Operate the device at lower power so that you do not
experience higher temperature that cause the "collapse".
This
temperature operating threshold is very process specific, which addresses
the other point in your question: TQHBT
If I am not mistaken,
TQHBT is a Heterjunction bipolar transistor manufactured by Triquint
(Google Search as I had never heard of the device). In this case, they
should provide you information on temperature operating ranges for the
device to avoid the "collapse" phenomena.
To be honest I am not
entirely versed in the physics of the collapse, so I can not tell you
exactly if the mechanism is due to beta-temperature effects of say carrier
mobility effects, etc. Maybe someone else can shed light on that.
_________________
CMOS RF and Analog ESD Specialist!
www.srftechnologies.com
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satish.1979
Post subject: ThanksPosted: Wed Oct
11, 2006 8:59 am
Captain
Joined: Tue Oct 03, 2006 3:03
am
Posts: 11
Location: India
Thanks stephan for your kind
and brief reply
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Jeanalmira
Post subject:
Posted: Mon Oct 30, 2006 10:37 pm
General
Joined:
Tue Mar 15, 2005 11:43 pm
Posts: 65
Location: Singapore
Hi
:
How about GaN HEMT? I observed that it happens to GaN HEMT
too. I am not sure whether it's related to surface trapping? and how
this phenomenon related?
Any advice is appreciated.
Thanks and Regards,
Jean
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Stephen
Post
subject: Posted: Thu Nov 09, 2006 6:48 pm
Captain
Joined:
Wed Jun 21, 2006 8:33 pm
Posts: 21
Location: Queen Creek, Arizona
Jeanalmira,
I think most of my previous comments still apply.
the phenomena is a temperature dependent effect and is possible among
multi-legged devices. regarding any particular technology, you need
to ask your foundry for detailed information on the conditions over
which the collapse may occur. Overall, remember it is caused by non-uniform
temperature gradients across the legs of your device.
Keep temperature
low and uniform across the device, and use a very uniform layout; is
the best advice I can give without specific knowledge of the process.
_________________
CMOS RF and Analog ESD Specialist!
www.srftechnologies.com
Posted 11/12/2012
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