Two-IC circuit combines digital and analog signals to make multiplier circuit

摘要

The circuits presented here use an analog switch-such as a DG419 or one-third of a CD4053-to combine an analog signal with a standard PWM signal. Most microcontrollers can easily generate the PWM signal. Combining the PWM signal with the analog signal and lowpassing the result effectively multiplies the analog signal by a digital value. Such a circuit can be useful in signal processing, power factor correction, automatic gain control, and sensor interfacing. All four circuit variants rely on the same principle: using the analog switch to adjust the duty-cycle ratio between two analog input levels, and a lowpass filter (LPF) to eliminate the PWM chopping frequency.