Arithmetic circuit forming logarithm or power of sum - has modulus and sign determining circuit connected to output of subtractor and feeding selector switch and function former

The arithmetic circuit is used for obtaining the log of a sum or differences , or for obtaining the power of the sum or difference for an exponent different from 1. The sum or difference is formed from at least two functions (f1(x1); f2(x2)) with each function or the respective variable (x1, x2) providing the inputs for the arithmetic circuit. The circuit comprises a subtractor (3) with two inputs for the respective input signals (log x1 log x2) followed by modulus forming circuit (4). The latter is connected to a sign determining circuit (4) which controls a changeover switch (7). The switch allows either of the input signals (log x1, log x2) t be supplied to an adder which also receives the output of a function stage following the modulus former.