Discussion Forum

Hello,

I am trying to integrate a semiconductor simulation of BJT npn, with a circuit to examine it as a switch. For the pn diode circuit example COMSOL converts only one contact in a ciurcuit current contact (the other is left to 0 V) to use it as a voltage source between the circuit source and the resistance. In my case, I treated the BJT as two diodes then base and collector contacts are used as circuit current and the emitter is left to metal contact of 0V (ground, no related to the circuit). So far it has not converged or the result in the cut off region is not the expected (should be Vcolector=Vout=Vcc=5V). How should I configure the contacts of the BJT (which must be circuit current, which must be the positive node).

Actual configuration
Device Nodes Description
p n
Ground 0
Vin 1 0 Base source (0V for cutoff)
Rb 1 2 170kOhm
Rl 3 4 5kOhm
Vcc 4 0 Colector source 5V

semiconductor BJT
emitter contact, terminal type Voltage (0V)
base contact, terminal type circuit (current) related to external I vs. U1 with node p=2 n=0 (base emitter diode)
collector contact, terminal type circuit (current) related to external I vs. U2 with node p=3 n=2 (base-collector diode).

I tried a circuit simulation (BJT from ACDC module not from semiconductor simulation) and the result was the expected (5V=Vout=Vc), but the node configuration is not the same when coupling with the semiconductor BJT simulation.