Direct current differential amplifier arrangement, especially for the measurement of slowly varying weak voltages

摘要

1. Direct current differential amplifier circuit, particularly for measuring low, slowly varying voltages of the type having two operational amplifiers (A1, A2) in cascade, whereof the non-inverting inputs (a) are connected to the input terminals of the circuit, the first amplifier (A1) being relooped on to its inverting input (b), whilst its output (c) is connected to the inverting input (b) of the second amplifier (A2), the latter having a feedback loop (3) determining a predetermined gain thereof, characterized in that the non-inverting inputs (a) of the two amplifiers (A1, A2) are connected to said input terminals (b1, b2) of the circuit via switching means (1) in order to selectively permit the polarity reversal of said connection, in that it also comprises means (6) for determining the successive operating cycles involving a measuring cycle and a calculating cycle, a memory (7) for storing during each operating cycle the output signal (Vs1 ) of the second amplifier (A2) resulting from an input signal received in a first position of the switching means (1) and a calculating circuit (5) which, when said switching means are in a second position, receives the output signal of said second amplifier (A2) in order to operate during the calculating cycle, the subtraction of the stored signal and the second output signal of the second amplifier (A2), in that the outputs (c) of said second amplifier (A2) is connected to said calculating means and to said memory (7) via an analog-digital converter (4) and in that the calculating means and the memory are digital components controlled by a clock (6).