[Laser] New optical front ends

[F1AVYopto at aol.com]

I test two new front  ends based on the FET mu amplifier principle.
The gain seems very  strong.
The VLF schematic allows the use of the input FET at its Idss current  that 
gives the lowest input voltage noise available.
With 4 x 2SK170 FETs,  the noise is extremely low and the VLF sensitivity 
seems better than with my  others K3PGP RXs.
The BF schematic use only two FETs and seems to work very  well with small 
capacity photodiodes.
The 2,2M resistor can be increased but  the noise could be a little bit 
higher and you do sacrifice input dynamic range  with increasing gain.
Schematics are available at:  
http://pageperso.aol.fr/F1AVYopto/opto/Front+End+VLF+V1.jpg
http://pageperso.aol.fr/F1AVYopto/opto/Front+End+BF+V1.jpg
Theses  schematics could be improved and some components adjusted.
I look forward to questions and  comments.
73 Yves.