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Re: Low power pre-amp question



William,
Head room and Class A operation are the why. More efficency can be obtained 
with Class B but also more intermod. It is not an easy project.
Art , KC6UQH
----- Original Message ----- 
From: "William Leijenaar" <pe1rah@yahoo.com>
To: <amsat-bb@AMSAT.ORG>
Sent: Monday, June 26, 2006 1:24 PM
Subject: [amsat-bb] Low power pre-amp question


> Hi AMSATs,
>
> I have some unusual question about pre-amplifier
> designs.
> The idea is to make a high efficient transponder
> design that can run with minimum of battery power.
>
> To do so, I need every circuit "block" to run on as
> low power as possible. So I started with the first
> block, the 70cm pre-amplifier.
>
> I checked many design and ideas, but it is really
> amazing  how much battery power they consume. Typical
> designs use 10..30mA with some ~5V (collector-emitter
> / Drain-source) voltage. This makes it roughly
> 50...200mW battery power needed.
>
> Lately I have worked with some ISM IC's, and they run
> less than 20mA at 1.8V = 36mW for a total receiver
> (pre+mixer+pll etc)...
>
> I did some investigation, but I can not find out why
> current have to be so high for a good NF. Anyone knows
> a way to get a quit good NF (ultra low not needed)
> with low battery power consumption ?
>
> The best I found so far is the BFP520, with 2V@2mA=4mW
> With input signals that are not high above the noise
> level I still feel 4mW a lot. I am more thinking of
> micro-watts... if ever physical possible ????
>
> Maybe some hams have worked on this problem before,
> and I hope to share some information and toughts...
>
> 73 de PE1RAH
> William Leijenaar
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