Timer and Op-Amp conflict

[PreetamDas17]

I'm experiencing a weird problem. In the same circuit, a timer 555 and an Op-Amp cannot co-exist. It's giving a convergence error and the Assistant cannot solve the problem. I'm unable to design a pulse width modulator because of this error. Please help.

I'm using Multisim 13

[Chen_T]

Hi there,

Could you please post your circuit and I will help you check it.

Regards,

[PreetamDas17]

Okay, here it is. The circuit works fine without the timer, but when the timer is added, it's showing an error.

[PreetamDas17]

Is there any possible solution ?

[Chen_T]

Hi there,

Your circuit is OK, the erroer is due to the SPICE parameter settings. In analog and mixed-mode simulations, the circuit might be too complicated for the SPICE simulator to converge with the default settings and this is why the convergence assisstant is also included in Multisim. I suggest you run the Convergence Assisstant to see the log file.

Below is a list of these parameters and their significance

• METHOD 

Sets the time step integration method.

• Setting Initial Conditions to Zero

This step sets all the voltages of the circuit to zero as an initial condition for the solution.

• TMAX

TMAX is the maximum stepsize that SPICE uses; for default the program will choose the smaller of either Tstepor (Tstop-Tstart)/50.0. TMAX is useful when one wishes to guarantee a computing interval which is smaller than the printer increment, Tstep.

• RELTOL

Sets relative error tolerance of the program. The value must be between 0 and 1.

• RSHUNT

Value (in ohms) of resistors added between each circuit node and ground, helping to eliminate problems such as "singular matrix" errors. In general, the value of RSHUNT should be set to a very high resistance (1e+12).

• ITL1

Sets Operating Point Analysis iteration limit.

• GMIN

Sets min conductance (max resistance) of any device in the circuit (in mhos). Also sets value of the conductance that is placed in parallel with each pn junction in the circuit.

Hope this helps.

Regards,

[PreetamDas17]

Okay, I ran the convergence assistant tool and it displayed a similar window that you've posted, but when I click on Save, then close, the problem returns !