-
Phototransistor transimpedance amplifier
In the circuit shown in Figure 1, a sensor (represented as a current source) such as a photodiode is connected between ground and the inverting input of the opamp. The other input of the opamp is also connected to ground, so the non-inverting input becomes a. This provides a low-impedance load for the photodiode, which keeps the photodiode voltage low. The photodiode operates in mo.