Automatic stabilization of amplifier gain

The conventional method of measuring the voltage gain of an amplifier by equating it with the loss introduced by a calibrated attenuator is adapted to provide a continuous and automatic method of accurately defining and maintaining constant amplifier gain. The resultant arrangements are all forms of negative feedback systems and are characterized by high loop gain and the use of a precision attenuator in the ß network. Two types are distinguished according to whether the ¿error¿ signal representing the discrepancy between the input and attenuated output signals is made self-cancelling by being fed back into the amplifier, as in conventional feedback amplifiers, or used to control the gain of one or more of the amplifying valves, as in A.G.C. systems. Appropriate circuit technique is indicated and suitable applications of the method are briefly described.