Patent ID: 6255857
Filing Date: 2001-07-03
Classification: H03K

Abstract:
A signal level shifting circuit comprising:an input transistor having a base coupled to an input terminal for an input signal, a collector coupled to a terminal for a supply voltage, and an emitter;at least one diode coupling the emitter of the input transistor to a junction point for providing a level shifted signal;a bias circuit coupled to the junction point for conducting a current which flows via a collector-emitter path of the input transistor and via said at least one diode to provide a forward voltage drop of said at least one diode providing a level shift of the input signal;at least one transistor switch having a controlled path in parallel with said at least one diode; anda control circuit responsive to said supply voltage for controlling said at least one transistor switch to be non-conductive when said supply voltage has a first, relatively higher, value and to be conductive when said supply voltage has a second, relatively lower, value, the conductive state of said at least one transistor switch providing a reduced voltage level shift of the input signal when said supply voltage has the second value.