DIRECT EXTRACTION OF EQUIVALENT-CIRCUIT PARAMETERS FOR HETEROJUNCTIONBIPOLAR-TRANSISTORS

A new method is presented for the direct extraction of hybrid-T equiva lent circuits for heterojunction bipolar transistors. The method diffe rs from previous ones by extracting the equivalent circuit without usi ng test structures or numerical optimization techniques. Instead, ail equivalent circuit parameters are calculated analytically from small-s ignal S-parameters measured under different bias conditions. The analy sis includes the distributed nature of the HBT base. The calculated pa rameters are essentially frequency-independent and they exhibit system atic bias dependence over the typical operating range of the transisto r. Thus, the present method ensures unique and physically meaningful p arameters for transistor design improvement and large-signal circuit s imulation. In addition, the present method is much faster than the num erical optimization method.