[Ronja] Vacuum tube in Ronja preamplifier
gullik.webjorn at flysta.net
Fri Oct 12 20:32:58 BST 2007
>Lower noise figure. The input capacity doesn't have an effect on speed
>in the Ronja design.
How far are you from the target?
I would imagine the large Rin sets the noise factor.
Most optical preamps use a transimpedance amp, where
the Rin ( Zin) is very low, so that the noise contribution
from that is minimised.
A PIN diode similar to the one in Ronja, ( BPV10, OPA905 )
into a transimpedance amp gives a flat frequency response
almost to 100 Mhz, and a sensitivity of -30-36 dBm for
10 dB eye opening.
What power do you estimate reaches the standard Ronja PIN?
I see your point about vacuum tubes, given that you have a
VERY high Gm, noise seems to be set mainly by the 1:st grid,
and is divided by Gm.
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