An Electronic Square-Law Circuit
H McG Ross, A L Shuffrey · Journal of Scientific Instruments · 1948
A review is given of the operation of the usual square-law circuits, and a greatly improved method of operation is described. A suitable circuit is shown which may be used either to produce an output wave form which is the square of the input, or may be used to measure the mean of the square of the input voltage and hence its r.m.s. value. In order to obtain the required parabolic valve characteristic curves the input signal is applied simultaneously to two grids of a multi-grid valve which affect the electron stream in a multiplicative sense, thus giving the square-law output.