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Published May 8, 2006 | ||
In an effort to better combine the editorial content of our magazine with our newly developed and retooled on-line presence, we have decided to expand Harlan's RF and microwave engineering advice into a monthly feature that appears in Microwave Journal. Harlan has selected one question from his "Ask Harlan" column to be featured in the March issue. Harlan will be monitoring the responses and will ultimately choose the best answer to the question. Although all of the responses to the featured question will be posted on our web site, we plan to publish the winning answer in the May issue. You be the expert: The answers to the April Question of the Month are below Renuka Wekhande from RF Arrays Systems India Pvt. Ltd. has submitted this month's question: Dear Harlan, 2. What are the advantages of using a gallium arsenide (GaAs) heterojunction bipolar transistor (HBT) over a pseudomorphic high electron mobility transistor (PHEMT)? From: Clive McDonnell, Serco Defence Support Ltd. 1. Glass substrate and epitaxial wafer. 2. A single power source, horizontal operation and an all optical process. From: Bhavin Shah, Hittite Microwave Corp. 1. The major parasitic component for a MMIC housed in a QFN package is the bondwire inductance. 2. GaAs HBT can be run at higher current densities thereby increasing their output power over the PHEMT. HBTs are inherently more linear compared to the PHEMT. From: Elochukwu John Adisionu, Jonel Engineering Co. 1. MMIC is very useful in the exploration of heterostructures such as InAIAs/InGaAs. Modeling/designing of MMIC is done such as to take care of the following problems (parasites): problems associated with power handling; amplification problems; problems associated with pad compatibility; problems associated with signal tracking; chip response and stability; noise filteration problems; and electrical conductivity. 2. With GaAs, engineers/technologists can model MMIC of frequencies beyond 100 GHz. During the manufacturing of MMIC it is always observed that GaAs has the following advantages over PHEMT: good electron transport characteristics; small DC power dissipation; good high frequencies properties and high switching speed. | The winning response will win a free book from Artech House, along with an "I Asked Harlan!" t-shirt. In addition, everyone who submits a legitimate response will be sent an "I Asked Harlan!" t-shirt. If your response is selected as the winner, you'll receive a free book of your choice from Artech House. Visit the Artech House on-line bookstore at www.artechhouse.com for details on hundreds of professional-level books in microwave engineering and related areas (maximum prize retail value $150). Disclaimers: Microwave Journal reserves the right to determine the legitimacy of all responses. The determination of the winning response is not based on any set criteria and is based only on the opinions of the editors of Microwave Journal. Questions and answers submitted to Ask Harlan are collected for sole use by Microwave Journal and www.MWJournal.com. Names and company affiliations will be published with questions and answers that qualify according to our editorial policies. Email addresses are collected in case we need to contact you. Mailing address information submitted for the delivery of the T-Shirt is collected solely for this purpose. Email addresses and mailing addresses are not published and are not shared with any third party. This form is not a magazine subscription application nor a Website registration. For magazine registration services, please click here. Entry into the T-Shirt give away is while supplies last. | |
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