Use a photoelectric-FET optocoupler as a linear voltage-controlled potentiometer

摘要

You can use a photoelectric FET as a variable resistor or a potentiometer in combination with a fixed resistor. The H11F3M photoelectric FET has an isolation voltage of 7.5 kV, enabling you to safely control high-voltage circuit parameters. The nonlinear-transfer characteristics of these devices are problematic, however (Figure 1). To correct the nonlinearity, using a simple feedback mechanism as a potentiometer yields a linear response (Figure 2).