Abstract: A variable operation speed MOS transistor having a source, a drain and a gate with a plurality of contacts formed thereon. One end of the gate of the variable operation speed MOS transistor is connected to drains/sources of first MOS transistors, while the plurality of the contacts formed on the gate of the variable operation speed MOS transistor are connected to the drains/sources of second MOS transistors, which are of an opposite type to that of the first MOS transistors, and the source or drains of which are connected to Vcc. Input signals are supplied to the respective gates of the first and second MOS transistors in such a manner as to adjust the turn-on and turn-off speeds of the variable operation speed MOS transistor.

Abstract: A back-bias voltage generating circuit of a semiconductor device having a driving signal generating portion for receiving oscillating signals from an oscillator such as a ring oscillator and generating alternating high and low driving signals, a first pumping portion for charging the input driving signal at one electrode of a pumping capacitor so as to produce a voltage at the other electrode of the pumping capacitor lower than a back-bias voltage, a second pumping portion for charging another input driving signal at one electrode of a second pumping capacitor so as to produce a voltage at the other electrode of the second pumping capacitor lower than a back-bias voltage, a first switching portion being turned on by a voltage higher than a back-bias voltage and connecting the other electrode of the pumping capacitor to a back-bias voltage terminal when the voltage of this electrode is below the back-bias voltage, and a second switching portion being turned on by a voltage higher than a back-bias voltage and c

Abstract: A back bias generating circuit comprising a ring oscillator for generating a signal of alternating current waveform, a back bias generating section for generating a back bias voltage, the back bias generating section including first through third inverter gates for respectively inverting an output voltage from the ring oscillator, a pumping capacitor for inputting an output voltage from the third inverter gate at its one terminal, and a switching transistor for applying an output voltage at the other terminal of the pumping capacitor to a back bias terminal, the other terminal of the pumping capacitor being controlled, in accordance with a level of the output voltage from the ring oscillator, such that it is connected to a ground terminal to generate the back bias voltage, and switching transistor control section for controlling a voltage to be applied to the gate of the switching transistor in accordance with a level of the output voltage from the ring oscillator.