I need a differential output AC constant current source of around 100 or 200mA. Freq is around 20 Hz.
Can I build that using a pair of Howland Current pump ?
Or is there any reference design using any ADI parts ?
AD8016 and AD8017 are amplifiers with high output current.
Here are the links for their datasheets:
AD8016 - http://www.analog.com/static/imported-files/data_sheets/AD8016.pdf
AD8017 - http://www.analog.com/static/imported-files/data_sheets/AD8017.pdf
Also, an additional resource for current source circuits is AN-968. You can read it here - http://www.analog.com/static/imported-files/application_notes/AN-968.pdf
Hope this helps!