Japanese expression spelling doubt

/lang/, can you clear me up something about the Japanese language? The expression that is romanized "dame da", is there any proper way of spelling it? I've seen it with a mix of katakana and hiragana (ダメだ), solely hiragana (だめだ), mix of katakana with kanji (ダメ出) and solely kanji (駄目出). If I want to use kanji, what would be the correct way to do so? Are there any specific rules in this case that determine which spelling should be used?

Correct kanji:
駄目だ

I think it's more common to use katakana:
ダメだ

Also remember, it's an adjective in it's own right, not just "expression".

例：
OPはダメなヤツだ。
OPは駄目な奴だ。