Bias and Temperature Dependant Third Order Nonlinearity of GaAs DHBTs and its use in Extracting Thermal Resistance

The effect of various biasing conditions and temperature on third order two-tone intermodulation distortion characteristics of InGaP/GaAs microwave DHBTs is studied. The experimental results indicated that the variations in the third order nonlinearity characteristic dip are mainly due to changes in the DC current gain of the device at a fixed and relatively low collector current. Changes in the AC power gain (with bias and temperature) only become important at higher collector currents. These variations in the dip of the third order nonlinearity are used to calculate thermal resistance at low power optimal operating point of the dip. The results are compared with other methods of extracting thermal resistance from DC characteristics. This analysis has been reported for the first time and is important in understanding the non-linear characteristics of microwave device