I'm struggling with an amplifier design for a radio front end.
Ham 600 meter band (475kHz)
The antenna is a ferrite loop (can't change that) with a resonating capacitor on the primary, and a few turns on the secondary, so I have a pretty low input impedance.
I have several designs in spice, with common emitter and common base configurations, but I am struggling to get the noise below 300nV/Hz^1/2. I need to get the noise as low as practical, as my input signal is somewhere less than 300nV. Basically, how low can I really go in a practical sense? I need to stay with transistors that are currently available, vintage unobtanium won't work for me.
This is followed by a mixer and crystal filter with 200hZ bandwidth that is performing well, but the front end is just not hacking it. I keep orbiting the drain with gain and noise.
The amp has to run from 2.8V.
In the end, I will need three preamps for three antennas, and the ability to switch inputs quickly without hammering the IF, but that's a secondary problem.
So, can someone point me to a text, preferably available online (Kindle ok) so I can get through it this weekend?