A transimpedance amplifier, transimpedance amplifier( TIA), is a current-to- voltage converter; it is a converter that produces a proportional voltage from a small input current. The input impedance of a transimpedance amplifier approaches zero, and the output impedance should be as low as possible.
Transimpedance amplifiers are realized by operational amplifiers, which work with a strong feedback(Rf). For this purpose, a resistor is connected between the output of the operational amplifier and the negative input, into which the input current (-Iin) is also fed. Since the gain is extremely high, all current flows through the feedback resistor. The output voltage (Vout) is obtained by multiplying the input current and the feedback.
Transimpedance amplifiers are used wherever very low currents have to be converted into voltages. For example, in combination with highly sensitive sensors, with photodiodes, photodetectors and photomultipliers.