thread: SSL Origin .
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Old 12th December 2019
Originally Posted by toofanstudio View Post
Thank u for good review.
Are “Jfet” and “fet “ same ?!
And what is the other preamp product with this technology?!
I've seen a few discrete mic preamps using all jfets or fets, same terminology. It's the front end that sets the noise floor which is why most designs use the lower noise bipolar transistors like 2SB737.

Fets cannot produce the very low noise specs a bipolar transistor can at low impedances. They shine at impedances of 5k ohms or above, then they follow a noise plot nomograph for source impedance noise.

This is why a noisier fet opamp can produce less noise in a circuit with resistors above 10k ohms than a lower noise bipolar opamp can because the bipolar part will read the resistor noise as well as self noise.

Sometimes they teach this stuff in college EE courses, sometimes they don't. I'll be at NAMM this year so I'll try and pick the brains at SSL to get more answers.