[volt-nuts] Making a Reference IC

[Dave M]

I realize that better references are available.

I was thinking of resurrecting a long-defunct Fluke 731 that I have in the 
garage.  The reference IC is bad in it, and (1) I don't want to throw it 
away without a meager attempt at repair, and (2) I don't want to spend a lot 
of money on it because it's in pretty bad physical condition.

I was hoping that someone could lend a touch of advice on those old 
references.  I have a few 1N827A reference zeners, and a washtubful of 
transistors.  Maybe something could be cobbled together that would get the 
731 back in operation.  Maybe not to original specs, but close, which is 
better than nothing.

Thanks for your reply,
Dave M



Jack Mcmullen via volt-nuts wrote:
> Just thinking why would you reinvent a transistor/zener reference
> when the industry's voltage reference chips are in the $2.00 or less
> single quanities with performance far exceeding anything previously
> available in discrete components??
>
>
>
>
> -----Original Message-----
> From: Dave M <dgminala at mediacombb.net>
> To: FEBO Volt-Nuts <volt-nuts at febo.com>
> Sent: Sat, Sep 12, 2015 1:58 pm
> Subject: [volt-nuts] Making a Reference IC
>
>
>
>
> I was looking at the schematics for the Fluke 731 and 732 voltage
> references.  these, and several other brands and models of voltage
> references, use the same or similar reference ICs as their basis.  The
> reference ICs are a Zener/NPN transistor pair on a single substrate.
>
> Please view in a fixed-width font such
> as Courier.
>
>        |
>        |
>      C |
>        |
>          |
>          |
>           |----
>           |  B
>          /|
>         / |
>      E |
>        |
>        +---------------
>        |
>     /------/
>       /
>      ------
>        |
>        |
>
> Just thinking... would it be possible to make a reference with similar
> characteristics with discrete components (a low tempco Zener and a
> transistor)?  They would likely have to be closely coupled thermally
> and
> maintained at a constant temperature within an oven or by a peltier
> device.
>
> What criteria would apply to the selection of the parts?
>
> Dave M