| 摘要 |
PURPOSE:To obtain an electrostatic protective circuit which is excellent in its withstand voltage/current performance and usable also in a roll call circuit, by forming a field-effect transistor with a drain, connected to its input terminal, and a source 15 and a gate 1g, provided with application of a prescribed voltage and next by forming a parasitic lateral bipolar transistor or the like connected in parallel with the field effect transistor. CONSTITUTION:This circuit is composed of the following parts: a field-effect transistor 1 having a drain 1d connected to an input terminal 2 and having a source 1S and a gate 1g provided with application of a prescribed voltage, a parasitic lateral bipolar transistor 5 connected in parallel with the field-effect transistor 1, and a parasitic resistance 4 due to an impurity region where a channel of the said field-effect transistor 1 is formed. Said parasitic lateral bipolar transistor 5 is operated by a potential difference generated across said parasitic resistance 4 upon the application of excessive input voltage opposite in polarity to said prescribed voltage. Hence the operation of the parasitic lateral bipolar transistor 5 enables the effective protection of an internal circuit against the excessive input voltage irrespective of current pulses and voltage pulses.
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