| 摘要 |
PURPOSE:To remarkably improve the measurement accuracy of the radiation measuring instrument by bringing plural current amplification use base ground transistors to cascade connection in a pre-amplifying part. CONSTITUTION:In this radiation measuring instrument, plural pieces of current amplification use base ground transistors TR1, TR2 which are brought to cascade connection as current amplifying circuit transistors provided on a pre- amplifying part 2 are used. In this case, the pre-amplifying part 2 is provided with a current amplifying circuit 5 consisting of an FET 1, an integration use capacitor Cf, two current amplification use base ground transistors TR1 which are brought to cascade connection to each other and an input additional resistance Rs against it, a second base ground transistor TR2, etc. In this case, the pre-amplifying part by which a temperature drift of the gain as a whole is much smaller than a conventional one can be constituted, therefore, the measurement accuracy of the radiation measuring instrument can be improved remarkably.
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