No Silicon Heaven then where do all the calculators go?

~ Emitter Follower Gain & Noise Calculator ~

Calculates the root mean square value of the Noise Voltage V_N(rms)at the Output of an Emitter follower [Common Collector Amplifier] ~ Are emitter followers noisy when used as input to pre-amplifiers ? ~ If the output impedance presented to the next stage is lower than R_S but the SNR is not affected very much is this an advantage ?

The Calculation does not take into account flicker noise and assumes perfect resistive loads and a modern silicon transistor with low noise bias and the transistor gain is constant within the measurement bandwidth defined

The circled nodes B C and E represent the external connections of the transistor and lower case r_bb and r_e and r_o are internal resistances but only r_bb produces thermal noise ~ r_o is included in the calculation but if not known assume its value is >1MΩ although for some PNP transistors it may be much lower

Start by entering a Collector Current and change other variables as required

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]
Base bias Resistor — R_B		Ω [ Base bias total resistance ]
Emitter Resistor — R_E		Ω [ affects input resistance R_in ]
Follower Load Resistor — R_L		Ω [ affects input resistance R_in ]
Source Resistor — R_S		Ω
Internal output Resistance — r_o		Ω
Intrinsic Base Resistance — r_bb'		Ω [ resistive base material produces thermal noise ]
Transistor d.c. current gain — β		[ also h_FE or 'beta' in some texts ]
Collector Current — I_C		mA Output Significant Figures
Device Temperature — T		˚C [ calculation uses ˚K ]
Noise Bandwidth — B_n		Hz Input Signal V_S
Calculated results using the values entered above
Signal to Noise Ratio — SNR		dB = 20 log (G_VV_S/V_Ntot) [SNR_OUT]
Maximum SNR due to R_S alone		dB = 20 log (V_S/√4 k T B_nR_S ) [SNR_IN]
Noise Figure — NF		dB = SNR_IN– SNR_OUT
Emitter Internal Resistance — r_e		Ω = V_T/I_CV_T= kT/q = mV
Common base current gain — α		= I_C/(I_C+I_B) I_B = I_C/β = µA
Amplifier input impedance — R_IN		kΩ = R_B∥ [ (r_bb'+(1 + β) (r_e+R_E∥R_L∥r_o) ]
Amplifier output impedance — R_O		Ω = (R_E∥r_o) ∥ [ (R_S∥R_B+r_bb')/(1+β)+r_e ]
Voltage Gain — A_V		V/V= (R_E∥R_L∥r_o) / (r_e+R_E∥R_L∥r_o)
Amplifier Voltage Gain — G_V		V/V= A_VR_IN/(R_S+R_IN)
Noise due to R_S∥R_B — V_NRS		nV_rms= √4 k T B_nR_S∥R_B × A_V nV/√Hz
Noise due to r_bb — V_Nrbb'		nV_rms = √4 k T B_n r_bb' × A_V nV/√Hz
Noise due to R_L∥R_o — V_NRo		nV_rms = √4 k T B_nR_L∥R_o nV/√Hz
Noise due to I_B through r_e — V_NIB		nV_rms = √2 q I_BB_n × (R_S∥R_B+r_bb'–r_e) × A_V
Noise due to I_C through r_e — V_NIC		nV_rms = √2 q I_CB_n × (R_E∥R_L∥r_o∥r_e)
Total Noise V at Output — V_Ntot		µV_rms = √V²_NRS+ V²_Nrbb'+ V²_NRo+ V²_NIB+ V²_NIC

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Keith Snook Transistor Noise references See these references for more about transistor noise :

The Art of Electronics 3rd edition chapter 8 ~ By Paul Horowitz and Winfield Hill
Noise in Transistor Circuits ~ By P. J. Baxandall ~ Wireless World November 1968
Designing low–noise audio amplifiers ~ By Wilfried Adam ~ Wireless World June 1989
Introduction to low–noise amplifier design ~ By A. Foord ~ Wireless World April 1981
The design of Low-noise audio frequency amplifiers ~ By E. A. Faulkner ~ The Radio and Electronic Engineer July 1968 ~ This excellent article along with the book 'Low-Noise Electronic System Design' By C. D. Motchenbacher and J. A. Connelly should answer most questions about electronic noise

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