A transimpedance amplifier (TIA) is an electronic circuit used to convert a current signal into a voltage signal. It is commonly employed in various applications, including optoelectronics, photodetectors, and sensor interfaces.
The primary function of a transimpedance amplifier is to measure and convert the input current into a proportional output voltage. The name "transimpedance" comes from the combination of "trans" (for current-to-voltage conversion) and "impedance" (the property that relates voltage to current in a circuit).
The typical configuration of a TIA consists of an operational amplifier (op-amp) with a feedback element, such as a resistor or a capacitor. The input current is connected to the inverting (-) input of the op-amp, while the non-inverting (+) input is usually connected to a reference voltage, like ground.
When current flows into the input terminal of the TIA, it creates a voltage drop across the feedback element. The op-amp adjusts its output voltage to ensure that the voltage at its inverting input (virtual ground) matches the reference voltage at the non-inverting input. As a result, the output voltage of the TIA is directly proportional to the input current.
The transimpedance gain (A_T) of the TIA is given by the ratio of output voltage (V_out) to input current (I_in):
A_T = V_out / I_in
This means that the transimpedance gain determines how much output voltage change occurs for a given change in input current. By adjusting the feedback resistor or other components, the gain can be set according to the requirements of the application.
Transimpedance amplifiers are widely used in various optical communication systems, such as fiber-optic receivers, where they convert the current generated by photodiodes (which detect incoming light) into usable voltage signals. Additionally, they are used in various sensor interfaces to convert current signals from sensors (e.g., photodetectors, photodiodes, transducers) into voltage signals that can be further processed by other electronic circuits.