Voltage-to-Current Converter Design with Precisely Defined Dead Band Voltage

Overview:

In the control of linear and nonlinear systems, small nonlinear features are sometimes intentionally embedded in closed-loop control systems. "Small" here means that the output of the embedded component begins to change linearly only if the input value exceeds a non-zero threshold. When the input value changes from zero to a threshold, the component's output value is zero. As a result, the embedding of the nonlinear element can suppress the damped oscillation phenomenon, and the damped oscillation phenomenon is a typical feature of the feedback system. The unipolar voltage-to-current converter shown in Figure 1 is constructed by a classic connection based on an op amp IC2a ​​and an NPN transistor Q1. The steady current passes through the emitter resistor RE, while the RE acts as a simple passive current-to-voltage converter. In a closed-loop system, the true negative feedback is the voltage that is applied to the inverting input of IC2a. The dead zone voltage of the volt-ampere characteristic is determined by the current supplied from the source of the reference voltage VREF and is grounded via resistors RD and RE. The source of the reference voltage VREF includes a bandgap IC1, a resistor divider Ra, Rb, and an op amp IC2b. (Please read the PDF for details)