Abstract: A square root signal extractor generates an output signal which is a square root function of an input signal. First and second diaphragm amplifiers have cascaded output chambers connected to a high gain output amplifier. The first and second amplifiers are connected as the non-inverting input and the inverting input respectively of the operational amplifier. A high gain output diaphragm amplifier is connected to the inverting amplifier output. The output diaphragm amplifier is constructed such that only a low level input pressure change is required to create a full swing of the output pressure. A non-linear input restrictor and a linear feedback resistor are connected to the input chamber of the inverting amplifiers. The feedback resistor has a significantly greater resistance than the input resistor. The non-inverting diaphragm amplifier is connected to the transmitter by a fluid repeater. A reference signal source is connected to the input restrictor and thus to the inverting input.