> ----- Original Message ----- > From: "Bob Barr" > To: > Sent: Sunday, October 21, 2001 1:09 AM > Subject: Re: [OT]: Multiple emitters and collectors > > > > Gerhard Fiedler wrote: > > > > > >At 09:52 10/21/2001 +1300, Jinx wrote: > > >>Was drawing up a couple of circuits and had an IC internal schematic on > > >>the desk for comparison. Many of the trannies in the IC schematic appear > > >>to have multiple emitters or collectors, others don't and are drawn > > >>conventionally. Seen them for years but never thought to ask before. Do/ > > >>can embedded trannies have multiple E/Cs ? Reasons ? > > > > > >Yes, they can. The reason is that a transistor is a three-dimensional > > >structure in a semiconductor block, with different donations creating > > >emitter, base and collector, one usually inside the other. So it's well > > >possible to create structures with multiple donation areas. > > > > > >The reason that they get used more inside ICs than as discrete parts is > > >probably that the usefulness of these multi-whatever parts is usually > > >limited to a very specific circuit. > > > > A very important reason is that if you have multiple emitters, they all are > having equal currents. Assuming the emitters have the same area; if not, you > can scale current ratio's by area scaling. That gives you easy way to set > ref/bias currents or to built current mirrors. > > Jan Didden > > > > > Could another possibility be that you get an increase in current handling > > capability by having multiple bond wires from the die to the package pins? > > (This may a way-off-base possibility. I don't know what range of wire > sizes > > is possible for the wire bonding process.) > > > > Does anyone know if discrete transistors are die-bonded with heavier wire > > than IC's? It almost seems that they'd have to be. > > > > Regards, Bob > > > > > > _________________________________________________________________ > > Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp > > > > -- > > http://www.piclist.com hint: The list server can filter out subtopics > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > > > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body