Abstract: The present disclosure describes embodiments of driver circuit. The driver circuit includes a first impedance element electrically coupled to a first inverter circuit and a second impedance element electrically coupled to the first impedance element and a second inverter circuit. For a first encoding using the driver circuit, the first inverter circuit and the second inverter circuit are controlled such that a first current flows through the first and second impedance elements, the first current having a first value and a first direction. For a second encoding using the driver circuit, the first inverter circuit and the second inverter circuit are controlled such that a second current flows through the first and second impedance elements, the second current having a second value and a second direction. The first value is substantially the same as the second value and the first direction is opposite to the second direction.

Abstract: A screw positioning device for a screwdriver comprises a connecting rod assembly, a screw positioning sleeve and a magnetic member. The screw positioning sleeve is axially defined with a slide hole for insertion of an end of the connecting rod assembly, the magnetic member is installed on inner peripheral surface of a front end of the screw positioning sleeve, the screw positioning sleeve is axially positioned at the end of the connecting rod assembly, and the positioning sleeve can move back and forth a predetermined distance with respective to the connecting rod assembly.

Abstract: The present invention relates to an extension rod assembly for a screw driving tool, which includes a base, a slide sleeve, a rear compression spring, a front compression spring, a fixing ring and a magnetic iron. The rear and front compression springs are disposed in the slide sleeve. When pushing the slide sleeve toward the tool head, the magnetic iron at end of the slide sleeve can provide a magnetic force to make the tool head pick up a screw to be screwed easily, besides, when pushing the slide sleeve toward the rod, the tool head will be caused to slide out of the slide sleeve, so as to facilitate replacement of the tool head.