An Improved dc Amplifier for Portable Ionization Chamber Instruments

摘要

It is widely recognized that the zero stability of dc amplifiers for measuring currents in the micro‐micro‐ampere region can be enhanced by the application of negative feed‐back. The promised advantages are often not fulfilled, however; and a design approach which emphasizes the economic exchange of amplifier gain for these benefits is outlined. In portable battery‐operated ionization chamber instruments, which are the main concern of this paper, it is not easy to achieve the loop gain needed for optimum performance; and a subsidiary reflexing scheme is adopted to overcome the limitation. In conclusion a practical instrument incorporating this improved circuit receives brief discussion and performance figures are given.