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Entry  Tue Mar 8 11:17:54 2011, Alastair, Laser, General, RF amplifiers 
    Reply  Wed Mar 9 09:31:50 2011, rana, Laser, Purchases, RF amplifiers : Cougars 
Message ID: 1345     Entry time: Wed Mar 9 09:31:50 2011     In reply to: 1344
Author: rana 
Type: Laser 
Category: Purchases 
Subject: RF amplifiers : Cougars 

The Cougar superiority comes from the low gain and high output level. Since it can put out ~20 dBm without distortion and has a gain of +10 dB, it can handle inputs with +10 dBm.

The other two amps can only handle inputs of around -10 to -5 dBm before they saturate highly. So the true noise performance is actually worse for those once you consider our setup:

namely, that we have a gain of 10 opamp ahead of it which is putting out ~20 nV/rHz of noise at all times. So the difference between 1 dB NF and 3 dB and 5 dB is totally inconsequential. The 3 dB NF is just an input noise of 1 nV/rHz.

In reality, the transmission readout doesn't need any of these since the signal is so large. The PDH diodes will have in-loop signals of somewhere between -10 and 0 dBm going into the Cougar. I believe we can only use those high gain, low output power RF amps in the case where we have very low light.

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