Hints & Tips

Q. How can I obtain Fmax, Gmax, Upg and K factor plots from s-parameter measurements.

A. Typically, UTMOST III s-parameter module is used to measure the FT versus IC (collector current) characteristic of bipolar transistors. The FT_CE routine can also be utilized to extract important parameters such as Fmax, Gmax, Upg and K factor. These parameters provide a clear indication of the performance of the device as an amplifier.

Brief description of these parameters as follows:

GMAX (Maximum Available Gain):

GMAX is the forward power gain when the input and output are simultaneously conjugately matched. GMAX is only defined for an unconditionally stable device. (K > 1).

FMAX : The frequency where GMAX gain is equal to 1.

K (Stability Factor):

K is a measure of oscillatory tendency. For K < 1 the device is potentially unstable and can oscillate by the application of some combination of passive load and source admittances. For K>1 the device is unconditionally stable. K plays an important role in amplifier design.