Transimpedance amplifier measurements

Hi all,
I'm going crazy thinking on how to perform large signal measurements on a Transimpedance Amplifier.

Briefly, the problem is following: I need a current signal (i.e. a PRBS signal) to drive my TIA and perform eye diagram at output. Does it exist any instruments (like BERT or something) that could give me a PRBS current signal instead that a voltage signal as all of the commercial BERTs give?
Any suggestion from your experience on how to overcome the problem?

Thanks in advance...