This is a RTD sensing element requires astable current reference for excitation. In this voltage reference, along with two operational amplifiers, are used to generate a floating 1 mA current source. This is the figure of the circuit.
This is accomplished as follows. The op amp A1 and the resistors R1 through R4 form a difference amplifier with a differential gain (GA1) of 1 V/V (since the resistors are all equal). A 2.5V precision voltage reference (VREF) is applied to the input of this difference amplifier. The output of op amp A2 (VOUT2 ≈ V2) serves as the difference amplifier’s reference voltage.
This is accomplished as follows. The op amp A1 and the resistors R1 through R4 form a difference amplifier with a differential gain (GA1) of 1 V/V (since the resistors are all equal). A 2.5V precision voltage reference (VREF) is applied to the input of this difference amplifier. The output of op amp A2 (VOUT2 ≈ V2) serves as the difference amplifier’s reference voltage.
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