~ Transistor r_bb Calculated from data sheet figures ~

Boltzmann Constant — k	1.38062×10-23	J/K   [ Joules/Kelvin ]
Charge on a single Electron — q	1.60218×10-19	C   [ Coulomb or Amperes/sec ]
Noise Voltage referred to input — en		nV/√Hz   from data sheet
Collector current for en — IC		mA   from data sheet
Transistor d.c. current gain — β		hFE   from data sheet @ IC
Device Temperature — T		˚C  =  ˚K
Measurement Noise Bandwidth — Bn		Hz — Is not the –3dB BW as Here
Calculated results using the Variables entered above
Emitter Internal Resistance — re		Ω = VT/IC   VT= kT/q =  mV
Noise due to IC — VNIC		nVrms = √2 q IC Bn
Calculated Base Resistance — rbb		Ω     and the -ve answer    Ω?

The calculated rbb result must be positive [ and Green ] and the –ve answer negative for result to be correct ~ If the noise referred to the input is not measured in /√Hz but in a given bandwidth then B_n should be changed to match it but e_nunits must still be nV~ If an output is NaN [ Not a Number ] check inputs are all numeric and e_n is not too low or B_ntoo high

" Do you work it out one by one ~ Or played in combination "