| 摘要 |
PURPOSE:To prevent destruction of elements with a simple constitution by using a diode and suppressing an input voltage of a CMOS-NAND circuit within the maximum ratings. CONSTITUTION:When a CMOS-NAND element N2 is turned off, a potential at a terminal O2 is increased to a power supply voltage VDD, and a capacitor C2 is charged via a variable resistor R2 and a diode D2. Thus, a voltage at an input terminal g2 is increased as shown in figure A, the 2nd CMOS-NAND element N1 is activated at a point of time t2 where the voltage is restored to a cutoff threshold voltage VTH with time constant C2(R2+rd2) decided by the circuit constant, and when the loop gain exceeds 1, the on/off state is inverted and the element N1 is turned on. Although the voltage at the input terminal g2 is increased rapidly as shown in figure A, it is clamped instantly to the power supply voltage VDD with the presence of the diode D2, and the CMOS-NAND element is protected from the voltage destruction. |
