A magnetic field sensor, comprising: a magnetic field sensing element responsive to a changing magnetic field and configured to generate a magnetic field signal having an amplitude; a measured threshold module coupled to receive a positive peak signal and a negative peak signal representative of the magnitude of positive peaks and negative peaks, respectively, of the magnetic field signal, and configured to generate a measured threshold signal representative of a measured threshold value in between positive peaks and negative peaks of the magnetic field signal; a temperature coefficient module coupled to receive a temperature signal, representative of the temperature of the magnetic field sensor, and an amplitude signal representative of the amplitude of the magnetic field signal, and configured to generate a temperature coefficient signal representative of a temperature coefficient of the amplitude signal, on the basis of the temperature signal and the amplitude signal; a memory device coupled to receive and configured to store, at each one of a plurality of storage times, a respective value of the temperature coefficient signal and a respective value of the measured threshold signal; a threshold module coupled to receive from the memory device, at a calculation time, a stored value of the temperature coefficient signal and a stored value of the measured threshold signal, each stored at a selected one of the plurality of storage times prior to the calculation time, said threshold module being coupled to receive the temperature signal, coupled to receive the amplitude signal, and configured to combine the received stored value of the temperature coefficient signal, the received stored value of the measured threshold signal and the temperature signal to generate a calculated threshold value corresponding to the temperature of the magnetic field sensor, wherein the respective value of the measured threshold signal stored at each one of the plurality of storage times is representative of the measured threshold signal at a particular temperature; and a true power on state (TPOS) detector coupled to receive the calculated threshold value (120, 164f) and also coupled to receive a signal representative of the magnetic field signal, wherein the TPOS detector is configured to compare the calculated threshold value (120, 164f) with a signal representative of the magnetic field signal to generate an output signal (110a, 242a). a magnetic field sensing element responsive to a changing magnetic field and configured to generate a magnetic field signal having an amplitude; a measured threshold module coupled to receive a positive peak signal and a negative peak signal representative of the magnitude of positive peaks and negative peaks, respectively, of the magnetic field signal, and configured to generate a measured threshold signal representative of a measured threshold value in between positive peaks and negative peaks of the magnetic field signal; a temperature coefficient module coupled to receive a temperature signal, representative of the temperature of the magnetic field sensor, and an amplitude signal representative of the amplitude of the magnetic field signal, and configured to generate a temperature coefficient signal representative of a temperature coefficient of the amplitude signal, on the basis of the temperature signal and the amplitude signal; a memory device coupled to receive and configured to store, at each one of a plurality of storage times, a respective value of the temperature coefficient signal and a respective value of the measured threshold signal; a threshold module coupled to receive from the memory device, at a calculation time, a stored value of the temperature coefficient signal and a stored value of the measured threshold signal, each stored at a selected one of the plurality of storage times prior to the calculation time, said threshold module being coupled to receive the temperature signal, coupled to receive the amplitude signal, and configured to combine the received stored value of the temperature coefficient signal, the received stored value of the measured threshold signal and the temperature signal to generate a calculated threshold value corresponding to the temperature of the magnetic field sensor, wherein the respective value of the measured threshold signal stored at each one of the plurality of storage times is representative of the measured threshold signal at a particular temperature; and a true power on state (TPOS) detector coupled to receive the calculated threshold value (120, 164f) and also coupled to receive a signal representative of the magnetic field signal, wherein the TPOS detector is configured to compare the calculated threshold value (120, 164f) with a signal representative of the magnetic field signal to generate an output signal (110a, 242a).