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Мои соображения по поводу "a pair of parallelled BF862s in a bootstrapped bootstrap" - 2 штуки bf862 параллельно фотодиоду, как в даташитах от linear, только ещё потенциал стока следит за истоком.
интересует, как схема интегратор-дифференциатор работает на DC и что значит абзац:
2) Getting rid of the DC and low frequency photocurrent without using
resistors. I made a BJT current sink degenerated with 4 diodes in
series with the emitter. Using N diodes reduces the transconductance by
a factor of N+1, and increases the equivalent shot noise voltage by
sqrt(N+1), so the resulting current sink runs 10*log(N+1) dB lower than
full shot noise--7 dB for 4 diodes. So far, so vanilla. The problem
was that the capacitance of the diodes dominated at low photocurrents,
which essentially doubled the 1 MHz noise at 40 nA. I used BFT25A C-B
junctions for the diodes, but that was the best I could get. I'd love
to figure out how to make fast, wide range, sub-Poissonian current
sources below 100 nA.
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Когда едешь на поезде - переезд всегда закрыт...
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"Interesting TIA design", специалисты,прокоментируйте.
Nov 12 2009, 16:48
