Large-signal characteristics of InP-based heterojunction bipolar transistors and optoelectronic cascode transimpedance amplifiers

A large-signal model for InP/InGaAs-based single HBTs incorporating soft-breakdown effects to the LIBRA Gummel-Poon (GP) model is developed and its validity is established from DC to microwave frequencies and over a wide range of input excitation levels. The large-signal characteristics of a cascode InP-based transimpedance optoelectronic preamplifier employing such devices are studied. Gain compression for the preamplifier was found to take place at an input power level of -20 dBm. Input power excitation varying from -65 to -5 dBm results in a degradation of the amplifier transimpedance gain of the order of 3 dBn. Experimental and theoretical characteristics are presented for the InP-based HBTs and transimpedance amplifier. Self-biasing effects are suggested as possible origin of the transimpedance variations with input power.