[volt-nuts] Matched resistors

[Todd Micallef]

I am not sure if Fluke had matched tempco spare parts, but you can look at
some NOS resistors from Fluke on ebay. They may be a good start and some of
the pricing isn't bad.

Todd


On Thursday, July 17, 2014, Randy Evans wrote:

> Frank,
>
> The high cost is my concern, although high performance demands high price
> typically.  I am trying to double the voltage reference from either an
> LM399 or LTZ1000, hence the need for precision matched resistors for a x2
> non-inverting amplifier (using a LT1151 precision op amp).  An alternative
> I am investigating is using the LTC1043 in a voltage doubling circuit as
> shown in Linear Technology app note AN 42, page 6, Figure 16.  It states
> that Vout = 2xVin +/- 5 ppm.  I am less concerned about the absolute
> accuracy than I am about the long term stability.  I assume that a high
> quality capacitor is required (low leakage, low ESR, low dielectric
> absorbtion, etc.) but the circuit does not appear to be dependent on the
> absolute value of the capacitors.  I'm not sure if the two 1uF caps  need
> to be matched.  If they do then that would be a show stopper.
>
> Does anyone have any experience using the LTC1043 in such a circuit?
>
> Thanks,
>
> Randy
>
>
> On Wed, Jul 16, 2014 at 9:40 PM, Frank Stellmach <
> frank.stellmach at freenet.de <javascript:;>
> > wrote:
>
> > Randy,
> >
> > resistor matched in T.C. are extremely expensive, as the manufacturer (or
> > yourself) would have to select these from a batch of many samples.
> >
> > reistors with very small T.C. (<1ppm/K) would do the job also, but they
> > also need to be stable over time, in shelf life opereation mode, i.e.
> > P<10mW.
> >
> > That means, you need those hermetically sealed VHP202Z from Vishay, T.C.
> > is typically < 1ppm/K and they are stable to < 2ppm over 5years. But they
> > cost already 80€ each, depending on tolerance.
> >
> > I made a longterm observation of these and found these parameters
> > confirmed.
> >
> > Frank
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