| 摘要 |
A signal level shifting circuit comprises an emitter-follower transistor with a base supplied with an input signal, a collector coupled to a supply voltage, and an emitter coupled via a level shifter to a bias circuit, whereby a level shifted signal is produced at a junction point between the level shifter and the bias circuit. The level shifter comprises one or more diodes to provide a forward voltage drop providing a signal level shift, a PMOS transistor switch in parallel with the diode(s), and a control circuit responsive to the supply voltage for controlling the switch to bypass the diode(s), thereby providing a smaller level shift, when the supply voltage has a lower one of two possible values. The circuit can have a differential input and a differential output stage, and cascode-connected transistors for reducing voltages so that the circuit can be implemented using BCMOS technology.
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