A bolometer circuit may include an active bolometer configured to receive external infrared (IR) radiation and a resistive load, which are configured to be connected in series in a bolometer conduction path from a supply voltage node to a common voltage node. A node in the bolometer conduction path between the resistive load and the active bolometer is coupled to a first input of an op-amp. A variable voltage source is coupled to a second input of the op-amp to provide a reference voltage level. The op-amp maintains the reference voltage level at the first input to generate a current flow in response to a resistance change of the active bolometer due to the external IR radiation. The amplifier circuit may be configured as a feedback amplifier or an integrating amplifier. The bolometer circuit may be configured to enable a low-power mode of operation.