Hi MrDEB,
& thanks for answering. Yes I would like to make a temperature controlled soldering iron. However, I would prefer to keep it analog (which a pic controlled iron is not, isn't that correct?) and have come up with the design shown in the attachment in post #1. I have now built a basic version of the circuitry (please see attachment to this post) and now see that it does not work as intended.
No matter what the voltages are relative to eachother (V- and V+ on the opamp), the voltage on the output of the opamp is never above 0,43 volts. But when I actively lift the voltage on the opamp's output to 5 volts (V1's output level - a 7805 IC) the output of the circuitry is about 0.6 volts below V2's voltage.
On all transistor bases and on the inputs to the opamp I have placed ferrite beads just in case there might be oscillations....
Any of you can help figuring out what is happening? It seems to be the opamp but it should be ok ...
Best regards,
Jesper