LNA DesignPeter WrightThe Law of Signal to noise Ratio With your First Gain Stageyou set therelationship of Wanted Signal to SystemNoise for everything that comes after. This first Gain stage should give you asmuch Gain as Possible.The Signal in General Is the Signal Bandwidth that gets Amplifiedto the Pass band 3bB Points ( Half Power ) The Amplifier amplifies every thing that itsees !IF! IF An amplifier sees a very strong signal onan adjacent channel say 10MHz awayitwill go into saturation and your weak RadioAstronomical signal will be lost . The onlysolution here isto reduce what theamplifier sees to Radio Astronomy Sources.How do you do this Design the feed to see nothing else (passband of the feed horn) Antenna design ingeneral (Trough , Corner Reflector)pointing to the Sky Binkers, Side wall .Or use a Filter Or kill the intruder with a notch filter( Resonant Stub)If You win somethingyou loosesomething else ! Yes If a filter is placed in frontof your gainstage it obviously has an attenuation of yourwanted signal . Here you can help by keeping this loss LowHelical Filter (Neosid) Interdigital filterFilter Silver Plated . The angle of your filter needs to be steep !Filter CurveForward Bias If a Semiconductor Junktion is open it willallow very weak signals to flow thatotherwise would not pass !Negative Forward biasThe power SupplyPre Amp !Buffer!A PHEMTPre AmpHybrid Technology :Negative Bias Transistor / MMIC 50 OhmRF Screeninghttp://www.schubert-gehaeuse.dePower Supply Via Coax The advantage of using the coax for poweris less cable and connectors . You do not inject unwanted signal into yougain stage UT141 Semi Rigic Coax and SMAConnectorsAs of Yesterday the NewTechnology !PHEMT MMICFromMinicircuitsBoth chips are optimized to be used together in a 2stage pre amp