Effects of spacer thickness on noise performance of bipolar transistors

The effects of spacer thickness on noise performance of a bipolar junction transistor with different emitter widths and operation frequencies are examined. The minimum noise figure (NFmin) derived from the Y-parameters as well as the base (r(B)) and emitter resistance (r(E)) obtained. from the device simulation is used as a measure of noise characteristics. Furthermore, the noise resistance (R-n), optimum source admittance (Y-sop), and the associated gain (G(A,assc)) are also given in this brief. To achieve the minimum value of NFmin, the spacer thickness should be targeted to an optimal value, and its value is frequency and geometry dependent.