Diode circuit fed with voltage follower doesnt work

It can be used but for most op-amps the maximum current you would be able to drive from the output will be limited to less than 50mA. Op-amps are not miracle workers! On the other hand you can attach an NPN and PNP transistor in a push-pull configuration and get more current: -

_{(source: northwestern.edu)}

Or, you could use an OPA541 - it is an op-amp and can supply up to 10 amps: -

I guess this one is a bit of a miracle worker!

Your third image is not a (source) follower, rather it is a common-source amplifier and generally is configured to provide gain > 1.

A source follower looks like this:

Note that there is no drain resistor at the top and that the output is taken from the source terminal rather than the drain.

\$V_{out}\$ will follow \$V_{in}\$ with a drop of roughly the gate threshold voltage of the MOSFET, \$V_{th}\$. This may be somewhere around 5V depending on the device, so one might reasonable choose a BJT emitter follower instead:

You can see the circuit is essentially identical excepting the transistor type. \$V_{out}\$ will follow \$V_{in}\$ with a drop of \$V_{BE}\$, typically only 0.7 V.

The input impedance of an emitter follower is relatively high, and it's output impedance is relatively low. So placed between a resistive voltage divider and the rest of the circuit (such as an amplifier input) has the effect of stabilizing the bias voltage developed across the divider against variation due to changes in current drawn from the divider.