Abstract: There is described a direct current meter with passive input and galvanic insulation, particularly for high voltage. The direct current meter is made up of a passive input part and of an active output part that is optically coupled to the passive part and electrically insulated from it. In this way the high voltage present at the input only affects the passive part of the meter, whereas the active part can be supplied with a low voltage and can be made capable to provide an output signal proportional to the current to be measured and substantially independent from the working temperature.

Abstract: The amplifier comprises a first field effect transistor controlled by the input signal of the amplifier and a current generator for the supply of said first transistor. The latter is biased so as to operate in its linear region and in cascade with it there is provided at least one second field effect transistor biased in a similar way, suitable for raising the output impedance of the amplifier, and thus its gain, to a value corresponding to the desired use.