Measurements and analysis of the optimisation of HBT circuits for optical demodulator designs

The second order non-linearity when using the base-emitter diode or the base-collector diode in an HBT for down conversion is analysed and measured. The non-linearity in the b-e circuit is shown to be at least /spl beta/ times larger than the b-c diode circuit (>90 times in the measured example). The contribution of the non-linearity of the current gain is identified. A circuit with added diodes is also examined.