An Experimental Investigation of Transistor Noise

Transistor noise is discussed in general and methods of measurement are presented. Experimental results show that noise figures for point-contact transistors are approximately 50 db; for junction transistors they may be as low as 10 db at 1,000 cycles. The effect of the variation of the dc operating point on noise figures and other parameters is discussed. It was found that the noise figure of point-contact transistors is relatively independent of the dc operating point, while for junction transistors it may vary considerably with the collector voltage and to some extent with the emitter current.