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Below are all of the forum threads, including all the responses to the original posts. 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? Top 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 Top 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 Top 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 Top 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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