This information is part of the Modelica Standard Library maintained by the Modelica Association.

This Differential pair model is one of the five benchmark circuits described in the SPICE3 Version e3 User's Manual (see information of package Spice3).

The differential pair circuit is operating in the differential mode. This means the input voltage VIN that is only applied at one transistor is amplified. To comprehend this behavior the user is recommended to simulate from t=0 to t=1s and observe "VIN.p.v" which is the input voltage and "Outputvoltage" which is the amplified output voltage.

Original SPICE3 netlist of the Differential pair:

SIMPLE DIFFERENTIAL PAIR

VCC 7 0 12

VEE 8 0 -12

VIN 1 0 AC 1

RS1 1 2 1K

RS2 6 0 1K

Q1 3 2 4 MOD1

Q2 5 6 4 MOD1

RC1 7 3 10K

RC2 7 5 10K

RE 4 8 10K

.MODEL MOD1 NPN BF=50 VAF=50 IS=1.E-12 RB=100 CJC=.5PF TF=.6NS

.TF V(5) VIN

.AC DEC 10 1 100MEG

.END

In the Modelica representation the tiny capacity CJC was set to 1e-9F to get a higher numerical robustness. The numerical behavior needs to be analysed before the original value CJC=.5PF can be applied.

MOD1	Value: Type: ModelcardBJT Description: Modelcard for transistors Q1 and Q2