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https://designers-guide.org/forum/YaBB.pl Design Languages >> Verilog-AMS >> Why current through the resistor changing https://designers-guide.org/forum/YaBB.pl?num=1427898710 Message started by ruwan2 on Apr 1st, 2015, 7:31am |
Title: Why current through the resistor changing Post by ruwan2 on Apr 1st, 2015, 7:31am Hi, I simulate the following code with SMASH. Code:
I get the transient of the logic and resister current as in the picture: The current through the resistor from 0 increasing to larger, although the voltage I think changes in the same way with time. How to understand the current curve? Thanks, |
Title: Re: Why current through the resistor changing Post by Ken Kundert on Apr 1st, 2015, 11:14am You are concerned about a 2 zepto Ampere current? That is 9 orders of magnitude smaller than iabstol. It seems to me that rather than being concerned about "Why [is the] current through the resistor changing", you might ask the question "Why isn't the current through the resistor changing". It does not seem like your resistor is being driven at all. -Ken |
Title: Re: Why current through the resistor changing Post by ruwan2 on Apr 1st, 2015, 12:43pm Thank AMS expert. You exclude me one direction. Yes, my next question is why the digital buffer does not drive the resistor? It needs a d2a module to adapter between them? |
Title: Re: Why current through the resistor changing Post by Ken Kundert on Apr 1st, 2015, 1:46pm Yes, a connect module is needed. The simulator should have inserted one, or complained if it could not. It might also be that a connect module was inserted, but the connect module was not configured properly. -Ken |
Title: Re: Why current through the resistor changing Post by ruwan2 on Apr 2nd, 2015, 6:12am Hi, After several trials with the example, I am still puzzled about the resistor in the module. I have tested input value to resistor. It is found that it only accepts logic '1' or '0'. The current does change when there is one '1' at one of the two pins, but wire b logic does not show impact on the current. In the following code, Code:
The current image is as below: http://i58.tinypic.com/2jdjgvt.png I cannot figure out how the vertical axis values come out. Its maxim is Ampere? When a number, such as '19' instead of '1' or '0' input, there is the following error message: ERROR: instantiation of SPICE primitive 'resistor' failed (instance and model do not match: cannot connect a non-signal to the SPICE port 'SPICE Port', except "1'b1", "1'b0", "1" and "0"; actual expression has to be either a concatenation, or a part select or an bit select made of signals) Although wire b has logic '1' and '0', it does not change the resistor current in the image. Could you explain it to me? Thanks, |
Title: Re: Why current through the resistor changing Post by ruwan2 on Apr 2nd, 2015, 6:34am Here is a direct link to the image: |
Title: Re: Why current through the resistor changing Post by Ken Kundert on Apr 2nd, 2015, 10:44am No, I have never used Smash. It is odd that you never plot the voltage, nor have you given any indication that you have provided a mapping from logic value to voltage levels. -Ken |
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