A temperature sensor circuit and system providing accurate readings using a temperature diode whose ideality factor may fall within a determined range. In one set of embodiments a change in diode junction voltage (ΔVBE) proportional to the temperature of the diode is captured and provided to an ADC, which may perform required signal conditioning functions on ΔVBE, and provide a numeric value output corresponding to the temperature of the diode. Errors in the measured temperature that might result from using diodes with ideality factors that differ from an expected ideality factor may be eliminated by programming the system to account for differing ideality factors. The gain of the temperature sensor may be matched to the ideality factor of the temperature diode by using an accurate, highly temperature stable reference voltage of the ADC to set the gain of the temperature measurement system. The reference voltage may have a trim capability to change the gain setting voltage by a digital address comprising a determined number of bits, with the programmable range for the reference voltage corresponding to a determined range of ideality factors.