Gain and bandwidth characteristics of a variable-gain, actively neutralized bipolar differential pair

The gain and bandwidth characteristics of a neutralized bipolar differential pair are analyzed, and results are compared with measurements performed on three integrated circuit test cells. A simple two-port model of the neutralized pair is derived through application of signal flow and dominant pole theories. This model is fully capable of predicting gain and 3-dB bandwidth as a function of a bias current applied to control gain magnitude.