8-bit DA converted analog signal photoelectric isolation circuit

Since the output of the D/A converter is directly connected to the controlled object, it is easy to introduce interference through the public ground wire. Isolation measures must be taken, usually
using an optocoupler, so that there is only light connection between the two to achieve the purpose of isolation. jrcla! The coupler is composed of a light-emitting diode and a phototransistor packaged in
the same tube shell. , the input of the light-emitting diode and the output of the phototransistor have input-output characteristics similar to those of ordinary transistors. By using the linear
region of the optocoupler , the output voltage of the D/A converter can be converted into an output current by the optocoupler, thereby achieving analog signal isolation, as shown in Figure 27-19. The output voltage of the converter is converted into an output current through a two-stage optocoupler, which not only satisfies the isolation of the conversion, but also realizes the voltage/current conversion. In order to obtain good conversion linearity and accuracy, two optocouplers with good linearity, the same transmission ratio and always working in the linear region should be selected during use.