| 摘要 |
PURPOSE: A plate potential stabilizing apparatus is provided to stabilize a plate potential by preventing a potential of a top electrode from being increased above a fixed level. CONSTITUTION: A reference voltage generator(20) generates a reference voltage. And a clamp circuit(30) is between the reference voltage generator and a top electrode(A), and compares the reference voltage with a plate voltage applied to the top electrode and then clamps the plate voltage when the plate voltage is increased above the reference voltage. The clamp circuit comprises a NMOS transistor whose gate is connected to a source in common by being connected between the reference voltage generator and the top electrode. The NMOS transistor has a threshold voltage between 0.1V and 5V.
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