Germanium transisors and gm

[Steve Eddy]

For silicon transistors, g_m is approximately 25/I_c. How does one go about calculating g_m for a germanium device?

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[sawreyrw]

Transconductance is given by

gm=q*Ic/K*T

where q=1.602e-19 (electron charge)
K=1.380e-23 (Boltzmann's constant)
T=Kelvin temperature (degrees Kelvin = degrees Cent + 273=300@ 23 degrees C)

This works out to about 38.5*Ic at 300 degrees Kelvin and is the same for both Ge and Si.

 

[Piercarlo]

Transconductance is given by

gm=q*Ic/K*T

This works out to about 38.5*Ic at 300 degrees Kelvin and is the same for both Ge and Si.

'Electron voltage" (or speed) is just 25,8 mV at 300 °K (usually rounded up to 26 mV). However, for pratical purposes, is convenient use 30 mV in order to take in account the effective working junction temperature (75-80 °C for non-stressing working condition of bipolar devices).

Hi
Piercarlo

 

[Steve Eddy]

Thanks guys!

se