Differential amplifier Calculator tool

R1 (KΩ) 
R2 (KΩ)
RC(Collector resistor) collector resistance (KΩ) 
RE(Emitter resistor) emitter resistance (KΩ) 
VP(Supply Voltage)Power source voltage (V)
Beta (DC Current Gain)Dc current gain
VBE (Base to emitter drop) base - emitter Pressure drop (V)
Rs(Source Resistance): Internal resistance of power supply (Ω)
RL(Load resistor) load resistance (Ω) 
fT(Current Gain BW Product):Current gain bandwidth (MHz)
CCB(Cu Collector-Base Cap.): collector add base Intermediate capacitance (pF)
CBE(Cπ, Base-Emitter Cap.): base add emitter Capacitance between (optional) (pF)

VC(Collector Voltage) collector voltage (V) 
VE(Emitter Voltage) emitter voltage (V) 
VB (Base Voltage) base voltage (V) 
IE(Emitter Voltage) emitter voltage (mA) 
IC(Collector Voltage) collector voltage (mA) 
IB (Base Voltage) base voltage (mA) 
gm (Transconductance)
rπ (Input Resistance of BJT at low freq)Transistor input impedance, low frequency (Ω)
re  (Ω)
RIN (Input Resistance of Amp)Amplifier input impedance (KΩ)
A (Amplifier Voltage Gain)voltage gain of the amplifier
fP1 (MHz)
fP2 (MHz)

VB=  VP*R2/(R1+R2)



Alpha= Beta/(Beta+1);

IC= Alpha*IE

VC= VP -  IC*RC/2



gm = Ic/25mA

re= Alpha/gm

rπ= Beta/gm

A=Alpha* rπ*RC/(Rs+2*rπ)/re




fT= gm/(2π*(CBE+CBC))

The lower pole is dominate: