A monitoring apparatus configured for monitoring a carbon brush of a brush holder assembly of an electrical machine. A silicon nitride film having a tensile stress is formed to cover the n-channel MISFETQn and the p-channel MISFETQp. In response to an interrupt from the real-time clock, the processor transfers control to an interrupt handling routine, which determines the interval of time that has elapsed since the previous real-time clock interrupt and increments the cumulative interval of time by the actual interval of time that has elapsed since the previous real-time clock interrupt. An embodiment of the invention further includes a plurality of capacitive elements configured such that the voltage support is applied to the gate of the drive transistor in phases rather than all at once to smooth voltage response to drive transistor switching.