The model SR240A 350 MHz Preamplifier is a 4-channel, DC-coupled instrument with a gain of 5 per channel. The amplifiers can be used independently or cascaded to provide gains of 5, 25, 125 or 625. The fast rise time, low noise, and DC accuracy of the SR240A make it the ideal instrument for use with photomultiplier tubes and photodiodes. The SR240A preamp is useful for amplifying small signals to levels that can be processed by other boxcar system modules. Typically, a signal of at least a few millivolts is required at the input of the SR250. If your detector does not supply this signal level, the SR240A can be used in front of the SR250 to ensure sufficient signal amplitude.