Since this topic has not been particularly SI related, here is a link. In switching power supply design the design of the inductive clamp (device speed and layout) often has a major impact on noise -- both voltage=20 and emissions. Curt Curt McNamara. P.E.=20 Senior Electrical Engineer=20 Logic Product Development=20 411 Washington Ave. N Suite 101=20 Minneapolis, MN 55401=20 Tel 612-436-5178=20 Fax 612-672-0443=20 curtm@xxxxxxxxxxx=20 www.logicpd.com=20 This message (including any attachments) contains confidential information intended for a specific individual and purpose, and is protected by law. If you are not the intended recipient, you should delete this message and are hereby notified that any disclosure, copying, or distribution of this message, or the taking of any action based on it, is strictly prohibited. -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Curt McNamara Sent: Wednesday, April 27, 2005 9:19 AM To: Christopher.Jakubiec@xxxxxxxxxxxx; roymesi@xxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: diode connected between source & drain - why? My experience with the body diode (as I understand it, a by-product of device construction) is that you *should not* depend on it to clamp an inductive kick-back. There is simply too much energy for it to=3D20 dissipate, and you will destroy the FET. Use an external diode clamp which is rated for the energy -- these should only cost a few=3D20 = cents. Curt Curt McNamara. P.E.=3D20 Senior Electrical Engineer=3D20 Logic Product Development=3D20 411 Washington Ave. N Suite 101=3D20 Minneapolis, MN 55401=3D20 Tel 612-436-5178=3D20 Fax 612-672-0443=3D20 curtm@xxxxxxxxxxx=3D20 www.logicpd.com=3D20 This message (including any attachments) contains confidential information intended for a specific individual and purpose, and is protected by law. If you are not the intended recipient, you should delete this message and are hereby notified that any disclosure, copying, or distribution of this message, or the taking of any action based on it, is strictly prohibited. -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Christopher.Jakubiec@xxxxxxxxxxxx Sent: Wednesday, April 27, 2005 7:44 AM To: roymesi@xxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: diode connected between source & drain - why? Hi Roy, When current is switching through an inductive load, a reverse EMF is generated when the current is turned off. This diode allows a path for this current in this situation. This body diode comes built into the MOSFET for free, and is not an extra device. A diode connected MOSFET behaves like a diode, while a standard connected MOSFET behaves like a switch with a diode in the body. -Chris -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Roy M. Sent: Wednesday, April 27, 2005 9:21 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] diode connected between source & drain - why? Hi, Can someone explain to me why are they Transistors (mosfets), that has a diode connected between the source and the drain? I tried to find something on the internet, but nothing... i don't understand what's the difference between a regular mosfet and a diode-connected-source-drain-mosfet. Thanks! Roy ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: =3D3D20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =3D3D20 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: =3D20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =3D20 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: =20 //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu =20 ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu