HR neuron model using analog computer technique

[zulqar]

Hi Everyone,

I am simulating(using HSPICE) HR neuron model using analog computer technique but I am not getting the required response.
I am using uA741 model of opamp and MLT04 model of multiplier. I have tested these components individually and they are working fine. I doubt there is something wrong in adjustment of DC levels.
If anyone can figure out what might be the problem , I will be extremely thankful.

 

[anorlunda]

What response are you getting and what did you expect?

 

[tech99]

View attachment 83872 View attachment 83873 Hi Everyone,

I am simulating(using HSPICE) HR neuron model using analog computer technique but I am not getting the required response.
I am using uA741 model of opamp and MLT04 model of multiplier. I have tested these components individually and they are working fine. I doubt there is something wrong in adjustment of DC levels.
If anyone can figure out what might be the problem , I will be extremely thankful.

Why don't you choose a more modern op-amp which has more perfect performance? The 741 is very obsolete. Small offsets etc can add up in a circuit like this.

 

[zulqar]

Why don't you choose a more modern op-amp which has more perfect performance? The 741 is very obsolete. Small offsets etc can add up in a circuit like this.

Thanks tech99 for the response.
Could you please let me know any modern opamp which I can use.

 

[tech99]

Thanks tech99 for the response.
Could you please let me know any modern opamp which I can use.

TL081 is possible. Most Op Amps have an offset adjustment, and I don't know if SPICE simulates this - maybe you have overlooked it if so.
One possibility with the circuit is that it is unstable and either oscillating, maybe at high frequency, or latching one way or the other. I think in hardware we would try breaking the signal path somewhere to see if it stabilises. I don't know the multiplier but I notice there is nothing to limit its high frequency response, so maybe SPICE will create noise or oscillation.