Which signal conditioning element uses PWM to adjust the voltage level?

• A. Saturation
• B. PWM (Pump and Heater)
• C. Transistor
• D. Amplifier

Answer: (B)

PWM, or pulse-width modulation, is the technique that adjusts the voltage level by varying the on-time of a switching signal. In a signal-conditioning block, a controller rapidly turns a switch on and off and the load (like a pump or heater) experiences an average voltage that is proportional to the duty cycle (the fraction of time the switch is on). By increasing or decreasing that duty cycle, you finely tune the effective voltage and thus the power delivered to the load, all with high efficiency since the switching element is either fully on or fully off.

This is why it’s the best fit for adjusting voltage: it directly sets the average output without needing a linear, dissipative method. Saturation simply limits output and isn’t a controllable method for voltage levels. A transistor is a switching element and can be used in PWM, but the technique itself is PWM. An amplifier changes signal amplitude in a more linear fashion and isn’t how PWM adjusts the load voltage.