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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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