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From: SNIPrf_man_frTHIS@yahoo.com (Frank Raffaeli)
Subject: Re: RF amplifier
Date: 28 Oct 2002 21:12:31 -0800
NNTP-Posting-Date: 29 Oct 2002 05:12:31 GMT
"David Thomas" wrote in message news:<4ccv9.1868$Mq.firstname.lastname@example.org>...
> I am a final year student in the UK and am about to start my project making
> an RF amplifier for between 1-2GHz. I can't seem to find much on the web for
> amplifierrs in this range. Does anybody know of any websites that may be
> useful to me, or have any example circuit diagrams of something similar? Any
> help would be appreciated.
> Dave Thomas
I'm going to make some assumptons:
Discrete silicon or SiGe, Single stage Bipolar, Low noise figure (<
2dB) Gain > 14 dB, 1dB compression +13 dBm, input/output z=50 ohms,
VSWR < 1.5 ....
Check the application notes for CEL (California Eastern Laboratories)
and Infineon. Consult books by Vendelin and Rohde. Get a freeware
package called Smith.exe from: http://www.rfglobalnet.com/
1) You will need to study S-parameters, matching and matching
networks. The Smith chart is an effective tool. Obtaining a really
good match from 1-2 GHz is non-trivial. Consider trade-offs. The input
match (S11) will probably be the most difficult.
2) You can use negative feedback to optimise noise and power match.
Alternatively, use a hybrid coupler at the input / output and use 2
3) Use the Smith chart and plot input/output impedance over a broad
range (not just the operating frequecy range). This is one effective
tool for analyzing the stability of the device.
4) Do a web search on the Infineon devices: BFP420, BFP520, and
BFP620. There are a lot of good write-ups and application circuits on
5) Optimise the bias network. There is a tradeoff between noise figure
and dynamic range / power capability.
Best of luck
Frank W. Raffaeli
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