Here's the LTspice simulation of the circuit I mentioned for 0 to 100% U2 pot rotation.
The Sziklai pair output gives a 3A maximum current.

The op amp can be just about any rail-rail output type.

If the load current is less than 200mA, then you only need Q1 and Q3.

@crutschow

Thanks Carl!!

My intention of using the buffer built as per post #9 above, was a failure. After ditching several very old potentiometers, I found finally it also had the output transistors reversed. A good design can do nothing against wrong hardware.

So in less than one hour your circuit was up and running. No rail to rail here so I used a TL071. The non-Sziklai version obviously worked at the first try, with a very small motor (current is around 30 mA).

As usual yours was a great help.

Gracias again.

 

No rail to rail here so I used a TL071.

That, of course, will limit the maximum output voltage.

 

That, of course, will limit the maximum output voltage.

@crutschow

Yes, sure. Being so small the motor (the current), I could go away with it and I even reduced the Vcc values.

@nsaspook

Almost ready now for moving to Switzerland and chase some bosons.

Stay safe.