Abstract: The present invention relates to a pull-up structure with variable strength, which combines a resistor network with N type MOS transistors. According to the invention, the pull up structure comprises an N-channel type MOSFET with a resistor in parallel. Alternatively, a resistor is connected between the terminal of the pull up and a voltage supply, or between the source of the N Type MOSFET and the terminal of the pull up, i.e. in series with the gate. This allows the pull up to be varied to compensate for process and temperature variations around a predefined pull-up strength, and at the same time provides low parasitic capacitance and a good dynamic response of the pull-up structure.