Using Conditional Logic to Display Sidebar Widgets on different product category lists

Hi really urgently need help as am getting totally lost with something I imagined was simple.

Have set up a very simple store which has a number of different product categories relating to products in different languages.

I need to be able to place widgets on the product category listing pages that are specific to those pages. Using widget logic I am using is_tax('category_name') to try and achieve this but it's just not working.

I'm sure I must be doing something pretty dumb and must be missing the obvious, can anyone help point me in the right direction?

Cheers