FI820F 3BDH000031R1 pin and its 3 pin false break, that is to say, TLC2652 pin 2 no current output, so there is I2 = I1. in other words is that we get a constant current output of 0.5mA at C. Since the measured voltage signal at the ends of the Pt resistance temperature sensor is weak, this voltage must be amplified by an amplifier circuit before A/D conversion.

FI820F 3BDH000031R1 amplifier circuit of the input signal between 50mV ~ 70mV, the A/D conversion voltage range of 0V ~ 2.5V, after calculating the amplification of the amplifier circuit for about 35 times can meet the requirements of A/D conversion. Ordinary operational amplifiers are generally more than hundreds of microvolts of input offset voltage, the temperature coefficient of the offset voltage is more than a few microvolts above zero. Although the input offset voltage can be adjusted to zero, but the drift is difficult to eliminate.

The FI820F 3BDH000031R1 provides an inexpensive solution to the problem of micro-signal amplification. The chopper-stabilised zero operation gives the TLC2652 excellent DC characteristics, with an out-of-phase voltage of 0.5 μV (typical) to 1 μV (maximum); an input out-of-phase drift voltage of 0.003 μV/°C (typical), and a long-term out-of-phase voltage drift of 0.003 μV/month [3][8]. After calculation, the performance parameters of the TLC2652 can meet the requirements of the measurement accuracy of this system, so the op-amp in the amplifier circuit of this system uses the TLC2652.