Level shift circuit which improved the blake down voltage

A level shift circuit comprising:

• first conductivity type first and second transistors having a current path whose one end is supplied with a second voltage higher than a first voltage corresponding to a high level of an input signal, each gate of the first and second transistors being cross-connected with the other end of the current path;
• a first conductivity type third transistor interposed between the other end of the current path of the first transistor and a first connection node connecting the other end of the first transistor and a gate of the second transistor, a gate of the third transistor being supplied with a constant voltage, one end of the current path and a back gate being connected;
• a first conductivity type fourth transistor interposed between the other end of the current path of the second transistor and a second connection node connecting the other end of the second transistor and a gate of the first transistor, a gate of the fourth transistor being supplied with a constant voltage, one end of the current path and a back gate being connected;
• second conductivity type fifth and sixth transistors interposed and connected between the first and second connection nodes and ground, each gate of the fifth and sixth transistors being complementarily supplied with the input signal;
• an output terminal connected to the first connection node;
• and
• second conductivity type seventh and eighth transistors having one end of a current path and a gate supplied with the constant voltage, the other end of the current path being connected to each back gate of the third and fourth transistors.

A bias circuit comprising:

• a first conductivity type first transistor having a current path whose one end is a node supplied with a second voltage higher than a first voltage corresponding to a high level of an input signal, and having a gate supplied with the input signal;
• a second transistor having a current path whose one end is connected to the other end of the current path of the first transistor;
• a level shift circuit generating the second voltage, the level shift circuit supplying thesecond voltage to a gate of the second transistor;
• a first conductivity type third transistor having a current path whose one end is connected to the other end of the current path of the second transistor, a gate of the third transistor being supplied with a constant voltage, one end of the current path being connected to a back gate while the other end thereof being connected to an output terminal;
• and
• a control circuit setting the back gate of the third transistor to a floating state when the second transistor is on according to an output signal of the level shift circuit, and setting he back gate of the third transistor to one of the constant voltage and the floating state when the second transistor is off.