Measure Transistor f_T,
Gain Bandwidth Product

Fixture

Fixture Schematic

Vrms in = 0 Set Vcc for VR1 = 1.00V = 10mA Measure VR2 = 327mV = 0.0327mA hfe = 10 / 0.0327 = 306

Compute f_T using h_feo x f_αe

AN139A Figure 5 Vrms In = 250mVrms data-4401.txt Columns kHz mVout Assume hfeo = hfe mVout at 100kHz = 647mVrms Plot kHz/1000 : 20*log10(mVout/647) fαe = 0.85MHz fT = 0.85 x 306 = 260MHz

Compute f_T using h_fe x f (f > f_αe)

AN139A Figure 4 Vrms In = 250mVrms data-4401.txt Columns kHz mVout mVout at 100kHz = 647mVrms = 6.47mArms Input Current = 6.47 / 306 = 0.0211mArms Plot kHz/1000 : (mVrmsOut/100)/0.0211*(kHz/1000) Per Plot, fT = 260 to 270 MHz

Example Oscilloscope Vout Measurement