Electronic Dimmable Transformers

[drive-thru9]

I am trying to make a 12V halogen desk lamp which is dimmable. I realise the easiest way is to get a 12V electronic transformer which is dimmable but I have a few questions about them...

Do they use regular lighting dimmer switches? What type of dimmer, specifically, do I need to get?
Is the dimmer switch placed on the mains voltage circuit or on the 12V circuit?
Anything else I need to know?

I am using a 20W halogen bulb (so a 60W transformer will suffice, right?)

Thanks

 

[breezer]

ordainairy dimmer, on the mains side, get the smallest wattage of transformer yo can.

incidentaly some dimmers wont work under 40 w so choose carefully

 

[drive-thru9]

ok, that's what I thought.
thanks a lot breezer