Code > Visual & replaced to &

Hello,
I have al little problem with tinymce editor.
I am wrting post in code and i have typed some [code] and there is a lot of && charaters. When i return to visual editor it looks the same as in code, but when i return again to code editing i got all && replaced to & amp;
How can i turn off that feature. It is good, but not for me.
Thanks.