[volt-nuts] Switches in integrating ADC

[setton at free.fr]

Many DVMs from the '70s or '80s (34740A/34750A, or the 3465x series) used discrete JFETS, for example from the 2N4392 or 2N4117 series. The 4066 and equivalent CMOS switches were far too leaky for this use. Many of these JFETS were selected for low leakage currents, such as the 1855-0412, selected from the 2N439x series, or the 2N4117A which is an off-the-shelf part. As usual, HP's manuals are your perfect source of information!

Joel Setton

----- Mail original -----
De: "John Devereux" <john at devereux.me.uk>
À: volt-nuts at febo.com
Envoyé: Lundi 14 Avril 2014 11:03:56
Objet: Re: [volt-nuts] Switches in integrating ADC

Jan Fredriksson <jan at 41hz.com> writes:

> What kind of switches are used in integrating ADC, ie to switch
> between voltage sources (ref and external) and to switch in multisloping
> resistors? FETs?

Yes, but I believe they are integrated ones usually. Either ye olde 4066
style or custom integrated circuits in the case of the HP 3458A.


-- 

John Devereux
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