A system of electronic analog computing is described in which current is used as the variable. The paper indicates that the circuit properties of transistors make them especially suitable for use in operational amplifiers for this computing technique. Experimental direct-coupled amplifiers are shown which have been built and evaluated using low- power, low-frequency transistors. The amplifiers have been employed under laboratory conditions to per form the operations of summation, scale-change, integration, and differentiation. The factors which determine computing accuracy are analyzed, and a new technique of error predic tion (based on square-wave output) is discussed. The paper concludes that the current-analog meth od promises to use transistors effectively.
A new technique of measuring low-power picosecond optical pulse trains