| 摘要 |
A circuit for a current source or a proportional to absolute temperature (PTAT) sensor or a bandgap regulator comprises at least two PTAT cells, the operating voltages of whose components overlap, and the sum of the outputs of the PTAT cells contributes to the output. One PTAT source comprises two transistors QH1 and QL1, operating at different current densities and providing a PTAT voltage between nodes E2 and E1 from the difference between their base-emitter voltages. The other PTAT source comprises transistors QH2 and QL2, also operating at different current densities and providing a second PTAT voltage between nodes E3 and E2 from the difference between their base-emitter voltages. The voltage output VSUM comprises these voltages added together and the base or emitter voltages of transistors QH2,QL2 lies between the potentials of the emitter and base of transistors QL1,QH1. The circuit may be implemented using complementary transistors (fig 4) or field effect (FET) transistors and in a CMOS process. The circuit may comprise stacked PTAT cells (Fig 6, fig 7) where the current passing through an emitter-collector path of one PTAT cell also passes through an emitter-collector path of another. The circuit can operate with low supply voltage, low noise and is insensitive to mismatches between transistors and between resistors. |
