In theory, you could use a DC-DC converter, but those are difficult to find and even more difficult to build yourself. And expensive.

If you can find one with 90% efficiency you will get about 1000 mA at 12 volts.

PS, it's 990 mA

But cheaper to just get the proper adaptor. They are cheap.

Is the fan expensive? If it's cheap, I'd just hook it up and see what happens. I ran a small DC motor designed for 3 volts at 5 volts for years. It ran fast, but didn't burn out. By its nature, a fan has good airflow to cool it.

A buck type switching regulator can be used to do this, but you have to design it. Linear Technology makes lots of them and they have very good data sheets and application to help you. See: www.linear.com

Another approach is to buy one, if you can find it.

YES, use LM7812 but output current will not bigger then 800mA .

Hi Guys i have an adapter with output of 16v at 800mA DC. I want the supply of 12v and 990mAh for my little fan. Can any one tell that how i can reduce the voltage of my 16v adapter to 12v.

And will this increase the amperes..???

If it increase then how much amperes i will get..?? Please help me out...!!!!

I shall be great thankful to you...!