FW: TopBand: High input intercept devices

[YO3CTK]

I'd say that one of the best solutions is to use a good old 2N5109 in
non-dissipative negative feedback circuit (patented by Norton). About 25mA
of collector current yields a +30dBm input IP3 with a very low noise and
50ohms input and output impedance. This arrangement has been used with great
success by Rohde&Schwarz in their EK070 VLF/MF/HF communication receiver.
The amplifier use a specially wound trifilar transformer, which is easy to
do after careful study of the patent.

Better yet, use two such amplifiers in push-pull, with hybrid
splitters/combiners. Works like magic.

73 de Mike, YO3CTK


-----Original Message-----
From:	Peter Chadwick [SMTP:Peter_Chadwick@mitel.com]
<mailto:[SMTP:Peter_Chadwick@mitel.com]> 
Sent:	None
To:	yo3ctk@alltrom.ro <mailto:yo3ctk@alltrom.ro> 
Subject:	TopBand: High input intercept devices

W5PS says;
>I saw a note from Carl, KM1H talking about how bad surface mount devices
>can be for intermodulation products. Thier is a company in California
>called Stanford Microdevices which manufacturers small inexpensive
>packaged MMICs in a micro-X package. They require +5v supply and have a
>IIP3 of +27dBm. These devices operate from DC (low freq) to 3Ghz. The
>part number with the mentioned IIP3 is the SNA-686 it costs about $5 for
>1 piece. They are Class 1 ESD sensitive since they are GaAs HBT devices.

Sounds prodigious! Usually, semiconductor amplifier manufacturers quote
output intercept, because it's a bigger number and looks better. Is it
really INPUT intercept they're quoting?
GaAs has problems with 1/f noise. Although it's improved over the year froma
noise knee of abt 200MHz 15 -20 years ago, I'd still be suspicous of  160
performance.
Having worked for a semiconductor company for the last 19 years, I am VERY
suspicious of their claims. they are usually the truth - but not 'the whole
truth and nothing but the truth'.
73
Peter G3RZP

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