A method to adjust an operating parameter of a magnetoresistive random access memory having a tunable circuit, such as a bias control circuit, provides for measuring the operating parameter, such as a word current or sense current, of the magnetoresistive random access memory to obtain a measured operating parameter result and tuning the tunable circuit, such as with trimmable resistors, based on the measured operating parameter result. A method is also provided to adjust an operating parameter of a wafer of magnetic random access memories each having a tunable circuit by measuring the operating parameter one or more of the magnetic random access memories to obtain a measured operating parameter result and tuning some or all of the tunable circuits based on the measured operating parameter result.