Unexpected Simulation Output

[neljoshua]

I am trying to run a simulation and am having problems.

The circuit is a basic amplifier. I would expect an output like this:

 but instead I get this:

I am not sure why there is not a rolloff at higher frequencies. My thought was that there is an issue with the SPICE model, so I looked for another SPICE model (text below), but I cannot seem to load it. However, when I press OK Fusion does nothing.

.model 2N2222 NPN(IS=14.34F XTI=3 EG=1.11 VAF= 74.03 BF=255.9

+ NE=1.307 ISE=14.34F IKF=.2847 XTB=1.5 BR=6.092 NC=2

+ ISC=0 IKR=0 RC=1 CJC=7.306P MJC=.3416 VJC=.75 FC=.5

+ CJE=22.01P MJE=.377 VJE=.75 TR=46.91N TF=411.1P ITF=.6

+ VTF=1.7 XTF=3 RB=10)

Any tips?

[abell118]

Hi Josh,

I used a different simulator - Multisim (with the 2N222) and got the results you were expecting. I waiting for AutoDesk to seem me the file but what you have should work. Upper 3dB point about 500 KHz and lower 3dB should be around 9Hz. Gain is 36.5dB. OBTW, I am wait for IT to load Eagle on my PC ...

Andy

[holger.vogt]

The output (gain, phase) strongly depends on the dc bias of the transistor (vcc, base and collector resistors) and any input or output capacitance chosen. Please show your circuit here.

According to the data sheet the transistor may amplify well beyond 100 MHz.

So you may extend the simulation frequency to see the output coming down again.