currenttovoltage

Current-to-voltage conversion is the process of turning an input electrical current into a proportional output voltage. It is widely used in sensors and signal conditioning where current signals must be interfaced with voltage-domain circuitry. The simplest method uses a resistor: the output voltage equals the input current times the resistance (V = I × R). This approach is inexpensive and passive, but it loads the source and offers a limited dynamic range and accuracy depending on the source impedance and supply voltage.

A more common and versatile method is a transimpedance amplifier, which uses an operational amplifier with a feedback resistor. The input current drives the inverting input, and the output voltage is approximately Vout = −Iin × Rf, with the sign depending on the configuration. This technique provides high input impedance, controlled gain, and low output impedance, making it well suited for detecting small currents from photodiodes or ionization detectors. A feedback capacitor is often added to stabilize the amplifier and limit bandwidth.

Other current-to-voltage schemes include specialized current conveyors or integrated transimpedance stages in microelectronic circuits. Design considerations include linearity, dynamic range, bandwidth, input-referred noise, input capacitance, and temperature drift. In practice, achieving a wide dynamic range while maintaining stability often requires careful selection of the feedback network and, for sensor applications, matching the conversion method to the source characteristics.

Applications span photodetection, fiber-optic receivers, radiation detectors, and current-sensing in power electronics. The choice between a simple resistor and an active transimpedance stage depends on the required sensitivity, speed, and impedance conditions.