Voltage follower with matched field effect transistors and matched current amplifying transistors for capacitor charging

Claim 1

A voltage follower comprising a first field effect transistor of which the gate is to receive the voltage to be monitored, a second field effect transistor which is matched with the first field effect transistor, a constant current generator connected to a coupling between the sources of the field effect transistors, a first current amplifying transistor of which the base is controlled by the drain of the first field effect transistor, a second current amplifying transistor which is matched with the first current amplifying transistor and of which the base is controlled by the drain of the second field effect transistor, a common current supply to the coupled emitters of the first and second current amplifying transistors, a pair of emitter follower transistors supplementing the first and second current amplifying transistors, the emitters of the emitter follower transistors being connected to a common and constant voltage through respective and equal resistors, a capacitor of which one terminal is connected to a constant voltage and of which the other terminal is connected to the gate of the seconD field effect transistor and is connected through a diode to be charged by the collector of the first current amplifying transistor, a current drain connected to the collector of the first current amplifying transistor, a connection from the collector of the second current amplifying transistors to a voltage of lower magnitude than or of the opposite sense to the voltages of the emitter or base of the second current amplifying transistor, and means for measuring the voltage developed across the capacitor.