** NPN BJT Differential Pair: The transfer Characteristic**



** Circuit Description (for the "common mode votage" Vcm = 10 mV) **

* two-rail power supply

Vcc 6 0 DC +5V

Vee 7 0 DC -5V 

* differential-mode signal level

Vd 101 0 DC 0V     ; this value is arbitrary, since we are going to sweep it  

Rd 101 0 1 

EV+ 1 100 101 0 +0.5

EV- 2 100 101 0 -0.5

* common-mode signal level

Vcm 100 0 DC 10mV

* use dummy voltage sources to monitor the collector currents of Q1 and Q2

Vic1 6 4 0

Vic2 6 5 0

* differential pair

Q1 4 1 3 npn_transistor_1

Q2 5 2 3 npn_transistor_1

* bias source

I 3 7 DC 1mA

* transistor model statement (VAf is the "Early voltage" of the device)

.model npn_transistor_1 NPN (Is=14fA Bf=100 VAf=100V)

** Analysis Requests **

* vary Vd from -300mV to +300mV in steps of 5mV

.DC Vd -300mV +300mV 5mV

** Output Requests **

.Probe

.end