sr555The SR554 is a low-noise, transformer-coupled preamplifier optimized for source impedances between 0.05 Ω and 1 kΩ. With an input noise of only 0.1 nV√Hz, the SR554 can be used in aCurrent amplifiers provide gain close to the experimental detector, allowing the user to minimize input cable length and its corresponding input capacitance. The SR555 minimizes noise and pickup before they permanently degrade