| 摘要 |
PROBLEM TO BE SOLVED: To stabilize the temperature characteristic of an input stage element in an electrometer circuit connected to an ionization chamber. SOLUTION: A JFET element 22 with two built-in circuits is composed of JFETs 18, 20, and a very weak current from the ionization chamber 10 is input into a gate of the JFET 18. Differential amplification is carried out between outputs of the LFETs 18, 20. A cooling element 30 is joined to the JFET element 22 in a close contact condition, and the JFET element 22 is cooled to keep a fixed cooled temperature by a temperature control part 34. Input resistance is increased thereby to be able to stabilize the temperature characteristic.
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