A very useful parameter in noise analysis of the bipolar transistor is the equivalent noise resistance. ( See the post on this quantity in this blog). However, another very important noise measure is the Noise Figure ( NF). The question is: What is the relationship between the two. The answer is very simple. NF = RN/RS. Where RN is the equivalent noise resistance and RS is the input signal source resistance. Please visit our website for more technical information and useful articles.