In simple terms, PWM involves rapidly switching the supply to the fan on and off, in this case 30 times a second, (30Hz). By altering the relative on to off times the average voltage "seen" by the ...

A PWM circuit for such systems can be implemented with three op amps on a single quad-op-amp chip (Fig. 1). Because op amps are used for the modulator, it's suited for a wide variety of applications.

An 8-bit digital/analog converter (DAC) can have 20-mV resolution from a PWM operating from a 5.0-V supply, and it's reasonable to require the AC noise on the RC filter's output to be less than a ...