Thermal Effects on Current Mirrors for High Speed Op Amps in Dielectrically Isolated Technology

Thermal effects on current mirror performance are significant. It is especially important to consider the thermal effects for current mirrors designed with dielectrically isolated bipolar devices. Thermal effects in integrated circuits can be categorized as thermal coupling, self-heating and the package thermal effect. This paper describes the effect of the self-heating on the output characteristics of the current mirrors. In general all the frequently used current mirrors in analog IC design are simulated and measured with the dielectrically isolated self-heating vertical bipolar inter-company (VBIC) devices. In a step by step procedure it is shown that this thermal effect is reduced or can be made negligible for the advanced mirrors; i.e. for the cascode connected and Wilson current mirrors.