Ref Diode temp compensation using 4 diodes

[ThermalRunaway]

Hi all,

I am using a 5.00V reference diode in one of my projects. Whilst reading the datasheet, I came across an application hint that suggested the use of four diodes to compensate for temperature changes. See attachment for details.

As it happens, temperature compensation is not a critical factor for my application, but I am curious as to how this 4-diode temperature compensation scheme actually works.

Can anyone with knowledge of this concept explain it to me?

Thanks in advance!

Brian

 

[ericgibbs]

hi,

Look at this.
(Zener Diodes - Some Interesting Characteristics)

Common diodes have a Vfwd drop reduction of approx 2mV/Cdeg.

 

[crutschow]

That 4 diode compensation is unique to the design of the LM136-5.0 reference. It's apparently related to the particular design and temperature characteristics of the reference. The -2mV/C change of a normal diode compensates the normal temperature coefficient of the reference. But you'd have to understand the specific circuit design and operation of that reference to see how the diodes actually provide that compensation.

 

[ThermalRunaway]

Thanks for the response both, much appreciated. Thanks for the link Eric. I also found lots of other references to a 2mV/Cdeg forward voltage drop for silicon diodes.

Cheers,

Brian