What is significance of capacative loading? - Page 1
Forum section: electronics / beginners

author: matrixofdynamism
author_rank: Regular Contributor
timestamp: February 19, 2023, 03:43:29 pm
content: Resistive loading is when resistor causes power dissipation from a power source, this could be a voltage source or current source. But what does "capacative loading" mean here? I understand that a capacitor charges up so the current draw reduces over time. But so what?

author: Doctorandus_P
author_rank: Super Contributor
timestamp: February 19, 2023, 04:37:10 pm
content: Capacacitive loading makes signals change slower.A very simple example is an I2C bus, which only has passive pullup resistors. If there is a lot of capacitance on the bus, then you have to reduce the pullup resistors to make them "stronger", or you have to reduce the data rate to give these resistors more time to charge the inherent capacitance on the bus.And when you have a faster system, this only gets worse.

author: BillyO
author_rank: Super Contributor
timestamp: February 19, 2023, 04:45:10 pm
content: Capacitive loads are reactive. It is the complex (as in complex numbers) impedance to an AC voltage. An ideal resistor has only real (as in real numbers) fixed impedance that does not change with frequency (or impulse or step). The impedance of a capacitor does change with frequency. This can be a difficult thing for some sources to deal with, like amplifiers for instance. With a capacitor the impedance goes down as the frequency goes up. Consider a complex (as in complicated) signal that has many different frequency components, like noise or a square wave. A capacitive load will have different impedances to those different frequency components and the loading will be different across the spectrum.A similar thing happens with an inductive load, except the impedance goes up as the frequency increases.

author: TimFox
author_rank: Super Contributor
timestamp: February 19, 2023, 06:31:24 pm
content: To calculate the effect of capacitive loading, you need to know the source impedance (for small-signal or linear behavior) and source current capability (for large-signal or switching behavior).The source impedance may also be a function of frequency.

author: matrixofdynamism
author_rank: Regular Contributor
timestamp: March 03, 2023, 09:22:59 pm
content: So what I have learnt is that, for pulse signals like we have in the digital domain, the capacative loading slows down the rise time and fall time of the signal. Also, different frequencies are attenuated by different amount which could be a significant issue in some other applications. I take this to mean that capacative loading is always a bad thing and not desired? What then is the way to mitigate it?

author: TimFox
author_rank: Super Contributor
timestamp: March 03, 2023, 10:57:16 pm
content: If you don't want to see changes from the source, or high-frequency content from the source, get to the load, then extra capacitive loading is a good thing.For example:A low-pass filter to limit the noise bandwidthA ripple filter to reduce the variations in power-supply voltage out of a rectifier

author: Terry Bites
author_rank: Super Contributor
timestamp: March 04, 2023, 10:59:08 am
content: Linear circuits:All amplifiers and most opamps will suffer stability issues with capacitive loads.www.analog.com/en/analog-dialogue/articles/ask-the-applications-engineer-25.html