<html><head></head><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><div id="yui_3_16_0_1_1457543596344_6244">Hi Brian,</div><div id="yui_3_16_0_1_1457543596344_5780"><br></div><div dir="ltr" id="yui_3_16_0_1_1457543596344_5781">All transistors have parasitic elements. There are parasitic elements among the Gate, Drain, and Source as well as between the Drain and Substrate and Source and Substrate. The "body" diode is one of the latter. It is formed at the PN junctions (definition of a diode) that exist between the Drain / Substrate and the Source / Substrate. Parasitics are undesired and scale with device size. Larger devices --> larger parasitics. An accurate board symbol showing all of them would be overwhelming and unnecessary, but semiconductor manufacturers do analyze them.</div><div id="yui_3_16_0_1_1457543596344_12117" dir="ltr"><br></div><div id="yui_3_16_0_1_1457543596344_11213" dir="ltr">So how big to make the transistors?</div><div id="yui_3_16_0_1_1457543596344_11467" dir="ltr"><br></div><div id="yui_3_16_0_1_1457543596344_11976" dir="ltr">Bigger --> more current capability<br></div><div id="yui_3_16_0_1_1457543596344_11977" dir="ltr">Bigger --> greater ESD immunity</div><div id="yui_3_16_0_1_1457543596344_11978" dir="ltr">BUT<br></div><div id="yui_3_16_0_1_1457543596344_14618" dir="ltr">Bigger --> switches more slowly (bad for logic) with more switching distortion (bad for power loads)<br></div><div id="yui_3_16_0_1_1457543596344_12703" dir="ltr">Bigger --> consume more die size, more expensive<br></div><br><div id="yui_3_16_0_1_1457543596344_12781">Hobbyist: switching small loads, slowly (turning LED's on and off at a few KHz, a few mA at a time) - Don't Care</div><div id="yui_3_16_0_1_1457543596344_9269" dir="ltr">You aren't pushing switching speed. Transient distortion will not be noticed. Size for load.<br></div><div id="yui_3_16_0_1_1457543596344_7368" dir="ltr"><br></div><div id="yui_3_16_0_1_1457543596344_7367" dir="ltr">Logic Designer: switching very small loads, very quickly (tiny currents at GHz)<br></div><div id="yui_3_16_0_1_1457543596344_8019" dir="ltr">Need for speed. Need for speed. Need for speed. Smaller transistors.<br></div><div id="yui_3_16_0_1_1457543596344_9270"><br></div><div id="yui_3_16_0_1_1457543596344_7971">Power Designer: switching large loads, slowly (power supplies - large currents at Hz, KHz)</div>Must have larger transistors to handle the mechanical stress of passing and switching large currents. You must manage parasitic distortion of your switching waveforms. Ripples in a bathtub are fun. Twenty foot tidal surges are not. You have the undying admiration of us "Logic" guys! :-)<br><br><div id="yui_3_16_0_1_1457543596344_15524" dir="ltr">Bottom LIne: The body diode in the symbol is a visual to tell you that this is a large transistor for higher power. It is like the horse on the hood. A ferrari, a car, can be used to go to Harris Teeter, but it has other capabilities. If you really have special requirements for this transistor, you should clearly show them in your documentation (minimum power, gate charge, etc.) A schematic should be a helpful document.<br></div><div id="yui_3_16_0_1_1457543596344_12230" dir="ltr"><br></div>Good Luck,<div id="yui_3_16_0_1_1457543596344_9532" dir="ltr">Kevin Schilf<br></div><br><div class="qtdSeparateBR"><br><br></div><div style="display: block;" id="yui_3_16_0_1_1457543596344_8329" class="yahoo_quoted"> <div id="yui_3_16_0_1_1457543596344_8328" style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div id="yui_3_16_0_1_1457543596344_8327" style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div id="yui_3_16_0_1_1457543596344_8330" dir="ltr"> <font id="yui_3_16_0_1_1457543596344_16226" size="2" face="Arial"> <hr size="1"> <b><span style="font-weight:bold;">From:</span></b> Shane Trent via TriEmbed <triembed@triembed.org><br> <b><span style="font-weight: bold;">To:</span></b> Carl Nobile <carl.nobile@gmail.com>; Grawburg <grawburg@myglnc.com> <br><b><span style="font-weight: bold;">Cc:</span></b> Triangle Embedded Devices <TriEmbed@triembed.org><br> <b><span style="font-weight: bold;">Sent:</span></b> Wednesday, March 9, 2016 10:43 AM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [TriEmbed] N-MOSFET Symbol<br> </font> </div> <div id="yui_3_16_0_1_1457543596344_8326" class="y_msg_container"><br><div id="yiv6669663074"><div id="yui_3_16_0_1_1457543596344_8325"><div id="yui_3_16_0_1_1457543596344_8324" dir="ltr">Brian,<div><br clear="none"></div><div>My understanding is that all power MOSFETs have a body diode due to the design and method of fabrication. However, small-signal MOSFETs typically do not have a body diode. I like to see the body diode on the symbol just to remind me that it is there.</div><div><br clear="none"></div><div id="yui_3_16_0_1_1457543596344_8323">Shane</div></div><br clear="none"><div id="yui_3_16_0_1_1457543596344_10380" class="yiv6669663074gmail_quote"><div class="yiv6669663074yqt0111640297" id="yiv6669663074yqtfd42618"><div dir="ltr">On Wed, Mar 9, 2016 at 10:26 AM Carl Nobile via TriEmbed <<a rel="nofollow" shape="rect" ymailto="mailto:triembed@triembed.org" target="_blank" href="mailto:triembed@triembed.org">triembed@triembed.org</a>> wrote:<br clear="none"></div><blockquote id="yui_3_16_0_1_1457543596344_10379" class="yiv6669663074gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div id="yui_3_16_0_1_1457543596344_10378" dir="ltr">Brian,<div><br clear="none"></div><div id="yui_3_16_0_1_1457543596344_10377">From my experience many symbols don't put in the diode even though they are actually in the part. In other cases they are not in the part. Sorry to say it seems to be a decision made by whoever creates the symbol. My own personal opinion is to put the diode in the symbol if the part actually has it and leave it out if it doesn't actually have it. I'm fairly sure that as of now most manufacturers put the diode in the part now, but there may be exceptions.</div><div><br clear="none"></div><div>~Carl</div><div id="yui_3_16_0_1_1457543596344_10382"><br clear="none"></div></div><div class="yiv6669663074gmail_extra"></div><div class="yiv6669663074gmail_extra"><br clear="none"><div class="yiv6669663074gmail_quote">On Wed, Mar 9, 2016 at 9:42 AM, Grawburg via TriEmbed <span dir="ltr"><<a rel="nofollow" shape="rect" ymailto="mailto:triembed@triembed.org" target="_blank" href="mailto:triembed@triembed.org">triembed@triembed.org</a>></span> wrote:<br clear="none"><blockquote class="yiv6669663074gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">I'm making an electronic symbols sheet for a summer Raspberry Pi class. Sometimes I see symbols that include the diode and sometimes without. The kids will be using a FQP30N06L or similar in one of their projects. Are there some MOSFETS that do not have the internal diode? Do I need to include both symbols and how would I differentiate them if I do?<br clear="none">
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Thanks,<br clear="none">
Brian Grawburg<br clear="none">
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