In some examples, an amplifier comprises a first integrator to receive a differential input signal, a second integrator coupled to the first integrator, a third integrator coupled to the second integrator, and a comparator to receive outputs of the second and third integrators, to compare each of the outputs to a reference signal that is below a power supply rail voltage supplied to the amplifier, and to produce an error current based on the comparison. The amplifier also comprises a feedback connection between the comparator and inputs to the second integrator. The feedback connection injects the inputs to the second integrator with a current that is determined at least in part by the error current.