Message	Date	From	Subject
177	2006-10-22 13:13:23	Steven S. Coles	Transconductance Equation Question
Hello, I thought "Radio Frequency Design" contained a form of Gm = n*Ie/26 In which n ~= 1 for germanium and a range (1.2 1.8?) for silicon. Now I can't find the form or range for silicon. I'd appreciate the correct equation and range. Thank you, Steven
179	2006-10-23 21:15:20	Wes Hayward	Re: Transconductance Equation Question
Hi Steven, et al, I'm not familiar with the form that you mention. The simple equation with gm=Ie/26 is one that holds for all sorts of materials. It is the first derivative of the common exponential expression for Ie(Vbe) which is the Ebers-Moll equation, a model that comes directly from the semiconductor physics. The number 26 is actually .026 when we deal with I in amps and is the ratio kT/q where k is Boltzman's constant, T is absolute temperature in Kelvin and q is the electronic charge in columbs. A good reference to this stuff is the text by Gray and Meyer. You make reference to "Radio Frequency Design." Did you mean "Experimental Methods in RF Design," or the earlier "Introduction to Radio Frequency Design," or something else? I don't recall having talked about anything other than the things that follow from the Ebers-Moll model, which is what is used in SPICE for all kinds of bipolar transistors, including Silicon parts and wild things like GaAs heterojuncti

Hi Steven, et al,

I'm not familiar with the form that you mention. The simple
equation with gm=Ie/26 is one that holds for all sorts of
materials. It is the first derivative of the common exponential
expression for Ie(Vbe) which is the Ebers-Moll equation, a model
that comes directly from the semiconductor physics. The number 26
is actually .026 when we deal with I in amps and is the ratio kT/q
where k is Boltzman's constant, T is absolute temperature in Kelvin
and q is the electronic charge in columbs. A good reference to
this stuff is the text by Gray and Meyer.

You make reference to "Radio Frequency Design." Did you
mean "Experimental Methods in RF Design," or the
earlier "Introduction to Radio Frequency Design," or something
else? I don't recall having talked about anything other than the
things that follow from the Ebers-Moll model, which is what is used
in SPICE for all kinds of bipolar transistors, including Silicon
parts and wild things like GaAs heterojuncti