| 摘要 |
PURPOSE:To prevent instability of oscillation frequency caused by the dispersion of protective resistors at semiconductor manufacturing process, by providing a limit resistor to a capacitance positive feedback circuit to an input terminal of an inverter of the 1st stage. CONSTITUTION:In an oscillation circuit consisting a plurality of inverters 11-13 in series connection, a resistor Rx is provided between a capacitor C charged/ discharged with an input signal (d) of the inverter 13 and an input terminal A. The resistance value of this resistor Rx is set to limit the voltage range of an input signal (a) of the inverter 11 within a power supply voltage VDD-Vss. If the signal (d) goes to 1 level, the voltage of the signal (a) rises to 1 level momentarily but this voltage is lower than the voltage VDD. Thus, the current path to the input protection circuit of the inverter 11 can not be formed. On the other hand, when the signal (d) changes from 1 to 0 level, the voltage of the signal (a) is higher than the voltage VSS. Thus, no current path to the circuit 31 can be formed. Then, no effect is given by protection resistors Rs1 and Rs2. |
