multiple thermistors - get max value

[Chupacabras]

Hi,
I have several thermistors (NTC) to monitor temperature inside enclosure on different heatsinks.
I want to control fan according to maximum value of those thermistors. Without MCU, just analog circuitry.
But I don't know how to get the highest value (voltage) of those thermistors.

I tried it with diodes, but it seems to be quite inaccurate.

Is there any way how to get "max" value of several analog signals?

[dmwahl]

Setting up an op-amp as an ideal diode (precision rectifier) will remove the error due to diode drop.

[mikeselectricstuff]

Might be worth looking at the R-T curve of the thermistor around the temps you're interested, and how that influences the effect of just wiring them in parallel.
You may find that simply wiring them in parallel will be close enough to achieve what you want. How much difference are you actually going to see between the 4 locations?

[Seekonk]

I've done a similar thing with open collector LM339 outputs in parallel, you get the lowest value.

[Chupacabras]

Setting up an op-amp as an ideal diode (precision rectifier) will remove the error due to diode drop.

Thank you!
That works perfectly
Exactly as I need