Diode vs Transistor

Many simple thermometers rely on a PN junction sensor because of its -1.8mv/c tempco.
All that I have seen use 1/2 of a transistor for the PN junction.
Diodes have the same tempco, so why aren't they popular for use as the sensor?
Are transistors cheaper than diodes, or is this some kind conspiracy?

A wandering mind needs to know.

They are not easy to bolt to things. I built an amp with 3 diodes in series mounted on the heatsink. It took two holes. Two diodes are a press fit and the other lays on top of the heat sink. Not good for production.

Bet you have never seen devices like this before: https://www.electro-tech-online.com/custompdfs/2013/02/AND8196-DPDF.pdf These have an independent diode and a transistor and a diode in the same package.

Jaguarjoe,

[A wandering mind needs to know. /QUOTE]

A transistor has a temperature sensitive Icbo current that can be amplifed by keeping the base resistance high, whereas a diode does not.

Ratch

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