Electronic Products

Differential Amplifier Calculator

This calculator calculate the bias voltage and current, as well as the gain and frequency response.

R1	(K ohms)
R2	(K ohms)
R_C (Collector resistor)	(K ohms)
R_E (Emitter resistor)	(K ohms)
VP (Supply Voltage)	(V)
Beta (DC Current Gain)
V_BE(Base to emitter drop)	(V)
R_s (Source Resistance):	(ohms)
R_L (Load resistor)	(ohms)
f_T (Current Gain BW Product):	(MHz)
C_CB (Cu Collector-Base Cap.):	(pF)
C_BE (C_π, Base-Emitter Cap.): Optional	(pF)

V_C (Collector Voltage)	(V)
V_E (Emitter Voltage)	(V)
V_B (Base Voltage)	(V)
I_E (Emitter Voltage)	(mA)
I_C (Collector Voltage)	(mA)
I_B (Base Voltage)	(mA)
g_m(Transconductance)
r_π (Input Resistance of BJT at low freq)	(ohms)
r_e	(ohms)
R_IN (Input Resistance of Amp)	(K ohms)

A (Amplifier Voltage Gain)
f_P1	(MHz)
f_P2	(MHz)

V_B= VP*R2/(R1+R2)

V_E= V_B-V_BE

I_E=V_E/R_E

Alpha= Beta/(Beta+1);

I_C=Alpha*I_E

V_C= VP - I_C*R_C/2

I_B=I_C/Beta

g_m= Ic/25mA

r_e= Alpha/g_m

r_π= Beta/g_m

A=Alpha* r_π*R_C/(R_s+2*r_π)/r_e

f_P1=1/(2*π*(R_s||2*r_π)*(C_BE/2+C_BC))

f_P2=1/(2*π*R_C*C_BC)

f_T= g_m/(2π*(C_BE+C_BC))

The lower pole is dominate: