Patent ID: 6624669
Filing Date: 2003-09-23
Classification: G09G

Abstract:
A drive circuit comprising a first power supply terminal, an input terminal for receiving an input voltage, an output terminal for outputting an output voltage, a first transistor having a source connected to said input terminal and a drain and a gate connected in common, a second transistor of the same conductivity type as that of said first transistor, said second transistor having a drain connected to said first power supply terminal, a source connected to said output terminal, and a gate connected to receive a voltage equal to a gate voltage of said first transistor, a first current control means for supplying a constant current flowing through a drain-source path of said first transistor, and a second current control, means for supplying a constant current flowing through a drain-source path of said second transistor,wherein said first current control means includes a first current control circuit connected between said first power supply terminal and said drain of said first transistor, and said second current control means includes a second current control circuit connected between said output terminal and a second power supply terminal, and further including at least a first switch connected in series with said first transistor between said input terminal and said first power supply terminal and on-off controlled for cutting off a current flowing between said input terminal and said first power supply terminal, a second switch connected in series with said second current control circuit between said output terminal and said second power supply terminal and on-off controlled for cutting off a current flowing between said output terminal and said second power supply terminal, and a third switch connected in series with said second transistor between said output terminal and said first power supply terminal and on-off controlled for cutting off a current flowing between said output terminal and said first power supply terminal.