| 摘要 |
PURPOSE:To reduce greatly the generation of ionization current for an output circuit consisting mainly of two MOS transistors connected in series, by transmitting the corresponding potential to the gate of the MOS transistor against impression of voltage in the direction where the MOS tansistor is made conduct to an output terminal when this terminal is set at a high impedance. CONSTITUTION:When a high impedance conversion signal phi is supplied, the gate potential of a TRQ1 is discharged through TRQ5 and Q6 and therefore set at the Vss level. Then the TRQ1 is quickly turned off and a TRQ2 is also turned off by a TRQ3. Thus an output terminal 3 can be set at a high impedance. The TRQ1 is usually kept off when the terminal 3 is set at a low level after the TRQ2 is turned on. Thus the output is set at a high impedance only with the TRQ3. The ionization current which is harmful to the operation of a semiconductor device is easily produced at a transistor having a high level of source-drain voltage. Such a transistor can be kept off to prevent effectively the generation of an ionization current.
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