On Wednesday 07 December 2005 06:04 am, Karel Kulhavy wrote: > Is it possible to make a passive network from coils and capacitors that > would approximate negated reactance of 6pF capacitor in the frequency > range from 1MHz to 10MHz? > > It has to be passive device because I want to use it to compensate out > capacitance of photodiode in low-noise broadband preamplifier.
You can use a Common-Base transistor to isolate the photodiode capacitance. National Semi. shows a circuit doing this based on their LMH6642 op-amp. http://www.national.com/dt/LMH_Qual.pdf see page #22 for the Common-Base isolate, LMH6642 data sheet shows the circuit as well. Karel, you might want to had this link to your web site, gives good overview of photodiode issues: http://www.national.com/onlineseminar/2004/photodiode/PhotodiodeAmplifers.pdf http://www.national.com/onlineseminar/2004/photodiode/photodiode_transcript.pdf The 'Anitcapacitor' reminded me of the 'Nonlinear Capacitor' , THAT Corp. App. Note 103: http://www.thatcorp.com/datashts/600034-1.pdf I always thought it was cool solution in search of a problem...
