Will a capacitor actually help to lessen the effects of ESD? Because, with rise time of about 1 ns, the frequency of the ESD signal will be well above the self-resonance frequency of the capacitor and it won’t act as a capacitor. Maybe it won’t actually help to reduce the transients.

Please share any insights on this topic to help me better understand.

  • \$\begingroup\$ A capacitor can help to improve ESD protection. It depends on the value and properties of the capacitor and the schematic of the complete circuit (protection and circuit you're trying to protect). I can use a capacitor such that it does nothing for ESD. I can also use a capacitor such that it improves the ESD robustness. Include your schematic! Also try to find out how a capacitor would help. What mechanism is behind the fact that it will help (or not). \$\endgroup\$ – Bimpelrekkie Feb 15 '19 at 11:09
  • \$\begingroup\$ I went into quite some detail on ESD protection that includes the use of capacitors: electronics.stackexchange.com/questions/203500/… \$\endgroup\$ – Peter Smith Feb 15 '19 at 11:17
  • \$\begingroup\$ Keep in mind that there is no such thing as "the frequency of the ESD signal". The energy is spread over a range of frequencies, some much lower than the resonant frequency of a capacitor. Don't oversimplify the problem. \$\endgroup\$ – Elliot Alderson Feb 15 '19 at 13:45

Yes, it probably does. An ESD pulse has very high voltage, still very low charge. If your finger+body would be represented as capacitor, it would be about 100pF, charged to (for example) 8kV.

\$ Q_{body} = C_{body}*V_{body} = 100pF * 8kV = 800nC \$

When discharging to a 100nF capacitor the voltage becomes:

\$ V = Q_{body} / (C_{body} + 100nF) = 800nC / 100.1 nF = 8V\$

I still would recommend also adding a resistor, it functions as RC filter as well then.

PS. the human body capacitance (HBC) is traditionally chosen as 100 pF


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.