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

Abstract

This paper presents the design of a VBE 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 VBE 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 VBE referenced current source. The circuits have been realized using dielectrically isolated bipolar junction technology (DIBJT) with the vertical bipolar inter-company (VBIC) model.