Lecture 10: Bolometers - Leiden Observatory
Lecture 10: Bolometers - Leiden Observatory
Lecture 10: Bolometers - Leiden Observatory
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
Detection of Light: <strong>Lecture</strong> <strong>10</strong><br />
Noise and NEP<br />
There is Johnson noise, characterised by the noise voltage<br />
VJ =< I 2 J > 1/2 R<br />
CASE 1: if VJ is added to the bias voltage, the dissipated power P<br />
increases and R decreases (because of the negative resistance coefficient)<br />
so the voltage across the detector decreases<br />
CASE 2: if VJ opposes the bias voltage, the dissipated power P decreases<br />
and R increases, so net voltage across the detector still decreases<br />
In both cases, the detector response opposes the ohmic voltage change<br />
resulting from Johnson noise (negative electrothermal feedback)<br />
=<br />
4kT f<br />
R<br />
(T ) < 0
Change language