Current to Voltage Converter Circuit:

A device that produces a voltage proportional to input signal current is called a Current to Voltage Converter Circuit. The circuit arrangement is shown in Fig. 36.27.

In this circuit, a photocell or photomultiplier tube that provides output current proportional to the light flux but independent of the load impedance, is connected to the inverting input terminal of the op-amp. R_s is the shunt source resistance. As there is a virtual ground at the inverting input terminal, current flowing through R_s is zero and, therefore, the entire input current i_s flows through the feedback resistor R_f resulting in the output voltage given as

The above equation clearly indicates that the output voltage is directly proportional to the input (source) current i_s.

However, in this circuit, the lower limit on current measure­ment is set by the bias current of the inverting input. Often a capacitor C_f is connected in parallel with resistor R_f for reducing the high frequency noise and the possibility of oscillations.

Applications:

One of the most common uses of the current-to-voltage converter is in sensing current from photodetectors and in digital­-to-analog converter applications.