Sequential operation differential current amplifier

Claim 1

A comparison device for currents provided with a differential current amplifier with offset compensation and with sequential operation according to a preliminary phase (Φ0) and first and second operating phases (Φ1, Φ2), said comparison device being connectable to a high voltage source (VCC), a low voltage source (VEE) and an intermediate voltage source and comprising: a first resistor (R1) connected between the high voltage source and a connection node (N) ; a first current source (I1) connected between the low voltage source and said node through a first switch (S1) closed during the first phase (Φ1) ; a second current source (I2) connected between the low voltage source and said node through a second switch (S2) closed during the second phase (Φ2) ; a first differential amplifier (A1), a first input (-) of which is connected during said operating phases with said node through a first capacitor (C1), the second input (+) of which is connected during said operating phases with the intermediate voltage source, and the output of which is connected with the first input by a third switch (S3) closed during the first phase; a second resistor (R2) having a high value with respect to the first resistor connected between said node and the intermediate voltage source ; and servo-control means operating during said preliminary phase (Φ0) for urging, when the first switch is closed, the voltage of said node to be equal to the intermediate voltage source and the current in the first resistor (R1) to be roughly equal to the current of the first current source.