What is an example of purely capacitive load device?

[Nora]

Hello-
What is an example of a capacitive load? Is there a device that would be purely capacitive? For example, a heater is a resistive load, a motor an inductive load.
Thanks in advance!
Nora

 

[Kral]

capacitive load example -patent

Nora,
The gate of a MOSFET is (almost) a purely capacitive load, since the gate-to source input resistance is hundreds of megohms. This also applies to the input terminals of most CMOS devices.
.
Upon initial application of AC power, the input to a capacitor input filter of a conventional power supply presents a momentary capacitive load, since virtually all input current flows into the capacitor, not the load.
Regards,
Kral

 

[Nora]

mosfet capacitance load

Thank you Kral.

The gate of a MOSFET is (almost) a purely capacitive load, since the gate-to source input resistance is hundreds of megohms. This also applies to the input terminals of most CMOS devices.

I don't understand this- could you explain it more? It sounds like a large impedance (infinite?) is also high capacitance.
Thanks!
Nora

 

[invent]

finding capacitive load

On the gate of the MOSFET is an oxide layer separating the metal layer and semiconductor layer hence the name MOS.
Ideally the oxide layer is an insulator, but there is a very minute current leakage through it (nA/pA). Therefore it can be said that the input resistance is very large.

Other capacitive load would include thing like piezo motor/actuators.

 

[Nora]

Re: Capacitive Load

Hello-
Would a piezo buzzer be capacitive also?
Nora

 

[invent]

Re: Capacitive Load

Nora,

Yes a piezo buzzer is also capacitive.

This link contains some information on piezo buzzer:
**broken link removed**

If you do a quick search on the net, you will find that specs of piezo buzzer contains the capacitance of the buzzer.