A portable ramp for motor vehicles molded from co-polymer where the ramp has a longitudinal spine extending through a grid, has a sloped portion and a horizontal upper portion to support a wheel of a vehicle. The restraining element protrudes from the seat belt, from only on one side thereof and the seat belt may be configured as a multi-layer seat belt forming a hollow space between the seat belt layers. Further, a plurality of wires which electrically connect a pad of the semiconductor chip, a lead, and a sealing body which does the resin seal of the semiconductor chip and the wires are also included. As a result, the offset voltage of the additional gain stage appears across the output of the input stage in the same polarity during chopper stabilization.