These instruments are capable to feed constant currents in the ranges from few picoamperes (pA) to several amperes (A); typical construction for use in the lower range of feed currents uses operational amplifiers.
ðiːz ˈɪnstɹəmənts ɑːɹ kˈeɪpəbəl tə fˈiːd kˈɑːnstənt kˈɜːɹənts ɪnðə ɹˈeɪndʒᵻz fɹʌm fjˈuː pˈiːkoʊˌæmpɛɹz pˈiː ɐ tə sˈɛvɹəl ˈæmpɛɹz ɐ; tˈɪpɪkəl kənstɹˈʌkʃən fɔːɹ jˈuːs ɪnðə lˈoʊɚ ɹˈeɪndʒ ʌv fˈiːd kˈɜːɹənts jˈuːsᵻz ˌɑːpɚɹˈeɪʃənəl ˈæmplɪfˌaɪɚz.