the adsense cpc ads are paid by clicks,how about the banner ads?you get paid for impressions,clicks or CPA?

Both image and text ads are a mixture of CPC and CPM, you can’t choose which one to display.

Google has been testing CPA ads for a while but I don’t think they are generally available yet.

Most sites don’t get very high CPCs

The banner ads still get payed by clicks too

CPA are now announced by google which is now handle thorough Google Affiliate Network.
CPC is greater for text ads and lower for image ads (Banners)