sr555The SR555 and SR556 are ideal low‐noise current preamplifiers for SRS’ lock‐in amplifiers, and can also be used for any other small current detection purposes.The SR555 is a low-noise, hh-bandwidth, fixed-gain current (trans-impedance) amplifier desned to work with SRS lockin amplifiers. Current amplifiers provide gain close to the experimental detector, allowing the user to minimize input