Design of VBE Referenced Bootstrap Current Source, Sensitivity, and Self-Heating Effect

This paper presents the design of a V_BE based bootstrap (self-bias) current source and self-heating effects on its performance. The performance of this reference circuit is measured by the sensitivity of the output current with respect to the power supply voltage. The self-heating effect on the base emitter voltage and the output resistance of a device is used to clarify the design requirements. Based upon the basic principle of the V_BE referenced bootstrap current source, several combinations of current sources and current mirrors are used for the design to compensate the self-heating effect that degrades the circuit´s sensitivity. Simulation and measurement results validate the design and show that the proposed current source has improved sensitivity and is less affected by self-heating over the conventional bootstrapped V_BE referenced current source. The circuits have been realized using dielectrically isolated bipolar junction technology (DIBJT) with the vertical bipolar inter-company (VBIC) model.