It's OK. I tried to mostly hide it in the existing light fixture.
Keithley electrometer. Solid state!
It has a 1e14 ohm range.
It's OK. I tried to mostly hide it in the existing light fixture.
Keithley electrometer. Solid state!
It has a 1e14 ohm range.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
So driving home I did the series inductance multiplier, (which has certainly been done before.)
So I_+* to collector, and to R_cb. And also at base, inductor to emitter L_be
--+---\ />----+--> I out | --+-- | | | | +-Rcb-+--L_be-+
Does that work?
George H.
ps
These ~10-100 mH inductors come in groups where the L/R time constant is about the same, one group with 1/3 milli-H/ohm and then
1 milli-H/ohm. Goes with price too... :^)Geo
Right, and turn it into an inductor... does anyone use such a thing? Unless I've got some high gain transistor I need a big L.. oh a Darlington inductor multiplier?.. I need to check my (rather thin) inductor parts drawers.
George H.
Oh, and a series resistor between the emitter and the cap will help stiffness and reduce the shot noise contribution. We make a way-sub-Poissonian laser driver in a similar way.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
That actually looks capacitive. ;)
The transistor works like a gyrator.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
But the transistor is off!
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Well, a cutoff transistor is capacitive. ;)
I was assuming that was the AC equivalent circuit.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
[...]
Oh, very fancy. I have a Rohde&Schwarz UVM Microvoltmeter. Very pretty design but I hardly have use for it anymore:
-- Regards, Joerg http://www.analogconsultants.com/
Huh, too many inversions on my part maybe?
OK so a good cap and the right resistor, that does make more sense.
I will say the modulation looked like a decent sine wave, which does make things much easier filtering-wise.
I'm not anywhere near shot noise.. just getting rid of ~40 dB at ~0.1 A. Anyway I'll give it a go. Series is easy in this case.
George H.
Right, sorry, my mistake. I've got a lot of good capacitors, so for me it's a good mistake. :^)
GH
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Hi Phil, so a tip31 with R_bc=500 ohm and C_be = 100uF worked like a ch arm. I could add one in series to my diode laser drive! Thanks.
I'm confused by the series resistor between cap and emitter. (Oh maybe I put it in the wrong spot!) So this,
--+---\ />--R_e--+--> I out | --+-- | | | | +-Rcb-+--C_be----+
and not this, (which I drew first)
--+---\ />----------+--> I out | --+-- | | | | +-Rcb-+--C_be--R_e--+
George H.
The top one is what I had in mind.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Wouldn't an inductance multiplier rather look like this?
----+---\ />------> I out | --+-- | | +-Lcb-+
... with the L between C and B, and with no R whatsoever?
Dimitrij
Ahh, OK. The resistance is the base-emitter 'resistance' plus the coil R. (I want to guesstimate the time constant.) I_c average ~200mA (for the led thing.)
George H.
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