Converge problem for multisim, fail for ADA4004, works for AD820AN

[rchchen]

Dear All

Here comes a problem, could I ask for help here? I am using MultiSim for analog device version.

I am trying to simulate a transimpedance circuit for a photodiode. And the circuit works for OpAmp AD820AN, but the convergence problem appears when the OpAmp is changed to ADA4004.

ADA4004 is actually the OpAmp that we plan to use.

Could anyone have a check on this? The enclosed file include the simulation circuit and library for ADA4004.

Thank you very much.

Best,

Richie 

[Tien_P]

Looks like this circuit is having problem with DC operating point which is run before the transient.  I got the circuit to work by setting all nodes to zero for the initial condition, select Simulate>>Interactive Simulation Settings, click the down arrow in the initial condition area and select "set to zero".

[rchchen]

Dear Mr. Tien P.

Could I ask if you can explain a bit why setting initial condition to zero will get the circuit work?

Thank you very much.

Best regards,

Richie 

[Tien_P]

The SPICE engine starts the simulation by running DC operating point and the result is used as the initial condition. If the SPICE engine failed to solve the DC operating point, changing the initial condition to a known value 0V can potentially fix the convergence problem. If you don't get any simulation results, usually this is an indication it's a DC operating point problem.

If you search online for SPICE convergence problem, there are many articles providing you with suggestion what you can do to help the SPICE engine converge.