Build a Low-pass filter Circuit Diagram

This  Low-pass filter Circuit Diagram is useful where fast signal acquisition and high precision are required, as in electronic scales. The filter's time constant is set by the 2 ohm resistor and the 1 µ capacitor until comparator No. 1 switches. The time constant is then set by the 1.5 ohm resistor and the 1 jtF capacitor. Comparator No. 2 provides a quick reset. The circuit settles to a final value three times as fast as a simple 1.5 ohm—1 µ¥ filter, with almost no dc error. 

 Low-pass filter Circuit Diagram