PTAT oscillators for low Q resonating sensors

It is generally believed that automatic gain control is necessary for making an oscillator stable against both voltage supply and temperature variations. First, we show that automatic gain control is, at least, questionable if low Q resonators must be used. Afterwards, we demonstrate that virtually perfect stability against voltage supply variations may be easily achieved by a proper biasing strategy. Finally we introduce the PTAT oscillators, which allow to improve stability versus temperature variations without automatic gain control.