RC circuit as LPD (and integrator)? How ?

[David Webb]

How is it possible that when input is zero volts in above circuit, the output voltage of RC circuit (LPF) doesn't drop down to zero ?

 

[chuckey]

The capacitor stores the charge when the pulse is present and slowly discharges when the voltage is zero. If another pulse comes in the capacitor charges up again. if there is resistance in the circuit in series with the charging voltage (the pulse) the capacitor will charge more slowly and may not get to the peak voltage of the pulse.
Frank

 

[BradtheRad]

Your diagram shows how a capacitor behaves when it charges from a low impedance, but can only discharge through a high impedance. As a result, it maintains its charge during idle gaps.

On the other hand, if it had a path to ground, then it will drop to zero as soon as the input goes low.

The right-hand circuit has a diode. The capacitor can only discharge slowly. This would be the situation in your diagram.

 

[David Webb]

Your diagram shows how a capacitor behaves when it charges from a low impedance, but can only discharge through a high impedance. As a result, it maintains its charge during idle gaps.

On the other hand, if it had a path to ground, then it will drop to zero as soon as the input goes low.

The right-hand circuit has a diode. The capacitor can only discharge slowly. This would be the situation in your diagram.

What simulator is this ?

 

[BradtheRad]

What simulator is this ?

It's Falstad's animated interactive simulator. Free to download and use at:

www.falstad.com/circuit