Attila Another example somewhat similar to the DMTD is the Receiver in a laser DMI (Distance Measuring Interferometer). A photomixer the typical implementation consists of a photomixer (eg photodiode connected between gate and drain of NJFET source follower with boostrapped drain) + linear preamp + manually adjustable gain differential amplifier (eg MC1590) + differential line receiver. The performance of this signal chain could likely be improved somewhat. The distance moved is equal to the integral of the change in beat frequency between a pair of orthogonally polarised laser modes. A reference channel with stationary parts provides the frequency difference signal between the 2 modes as produced by the laser. The beat frequency is typically a few MHz (eg ~ 2MHz). Input signal levels at the photomixer are typically a few tens of microwatts (eg 50 uW) or so.
The small signal gain of the BJT differential pair you show is actually 2R/[2*(kT/(e*(I/2)))] =IR/(2kT/e). Bruce > On 08 July 2020 at 14:25 Attila Kinali <[email protected]> wrote: > > > Moin, > > As some of you know, I have been allowed to give a tutorial on low noise > electronics > for this year's IFCS. As the whole conference has been turned into a virtual > one, > we were asked to record our tutorials and upload them. Additonally to the > conference > I decided to put my tutorial online for everyone to watch. You can find it at > http://time.kinali.ch/ifcs_2020_tutorial/ > Though, I have to honestly admit, I am not proud of it. There is too much that > I couldn't fit what should be in there, in in the 75' we were given. And > there is > quite a few things that I think I made too confusing. Nevertheless I hope it > can > be of use for some. Please let me know what you think, especially if you have > ideas > how I could improve the tutorial for the next time I'm giving it. > > > Attila Kinali > > PS: As this years IFCS is fully virtual, the registration is still open and > the > rates are IMHO quite reasonable: https://ifcs-isaf2020.org/registration > If it's still too much, you can pretend you are a student. Nobody is checking > this anyways. > > -- > Science is made up of so many things that appear obvious > after they are explained. -- Pardot Kynes > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
