concept is illustrated in fig6 in which a clock 12 applies a clock signal to a prbs generator 14 which in turn applies a pseudo random nulling signal to a chopper stabilized amplifier 16 prbs generators have been used in connection with spread spectrum communications such as frequency hopping radar carrier signals such applications require a synchronization of the prbs at both the transmitter and receiver the purpose is to obtain secure communications rather than to reduce noise a prbs has also been proposed in connection with digital to analog converters and analog to digital converters to reduce noise levels by dithering the signal amplitude non linearities in the circuit are reduced by varying the amplitude of the input signal in a random fashion prbs in general is known and is discussed for example in the lee and messerschmitt text cited above at appendix 10 a 34 maximal length feedback shift registers 34 pages 451 456 the present invention uses a prbs technique in a unique manner the only prior uses of a prbs to randomize a signal frequency was in spread spectrum communications systems in which a prbs at the transmitter is synchronized with a prbs at the receiver for the purpose of obtaining secure communications the present invention by contrast employs a single ended prbs signal for the purpose of imd noise reduction a preferred circuit for implementing the invention is.