Does this mean that the equation I have for a single plate capacitor isn't valid either? Ed -----Original Message----- From: Tsuk, Michael [mailto:Michael.Tsuk@xxxxxxxxxx] Sent: Monday, June 11, 2001 7:38 AM To: si-list@xxxxxxxxxxxxx Cc: ytang@xxxxxxxxxxxxxxxxx Subject: [SI-LIST] Re: Inductance of Via Yibing Tang wrote: > I use a formula to calculate the inductance of through hole via, > L=5.08h[ln(4h/d)+1] > However, I find that it is not suitable for small ratio of h to d. From this > formula,if decrease the ratio, I could get very lower inductance, even > negative. It makes no sense to talk about the inductance of a via in isolation. None at all. Inductance is a quality of a loop of current; without knowing where your return path is, you can't get a meaningful value for the total inductance. In any case, it seems that your formula isn't applicable to vias; this was discussed back in March. See: http://www.qsl.net/wb6tpu/si-list/0117.html > My question is how far I can go to low the inductance. You have two main choices: 1. Bring the return path vias closer to the signal via 2. Shorten the length of the via The effect of the diameter is relatively weak. -- Michael Tsuk Compaq AlphaServer Product Development (508) 467-4621 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: http://www.freelists.org/archives/si-list Old list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: http://www.freelists.org/archives/si-list Old list archives are viewable at: http://www.qsl.net/wb6tpu