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https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> Basic Curent Conveyor (CCII) operation https://designers-guide.org/forum/YaBB.pl?num=1322174547 Message started by ssp on Nov 24th, 2011, 2:42pm |
Title: Basic Curent Conveyor (CCII) operation Post by ssp on Nov 24th, 2011, 2:42pm Hi everyone, I have been bothered by the operation of the following second-generation current conveyor (CCII). In this case it decharges the capacity (arrow points the current direction of the current source). Althought, as I'm new to the integrated circuit world, I have difficulty analysing the behaviour of this circuit, and seeing what's the exact purpose of the OTA amplifier. Also, what should be the caracteristics of the OTA and why ? (ie. high gain?, large output swing ?..) ? Thanks for your help, ssp |
Title: Re: Basic Curent Conveyor (CCII) operation Post by buddypoor on Nov 25th, 2011, 12:44am Hi ssp, who has told you that the shown circuit is a CCII ? That's not true. A current conveyor has one (non-invertnig) high-resistance and one (inverting) low-resistive input. The last one acts as a current input - contrary to OTA properties. This current is internally "conveyed" to the output and appears there (mostly with a factor of unity) as an output current. |
Title: Re: Basic Curent Conveyor (CCII) operation Post by ssp on Nov 25th, 2011, 11:21am Hi buddypoor, thanks for your response. Actually, I see the caracteristics of a CCII in that circuit: Y = non-invertnig, high-resistance X = invertnig, low-resistance Z = current input, high resistance |
Title: Re: Basic Curent Conveyor (CCII) operation Post by buddypoor on Nov 25th, 2011, 11:42am ssp wrote on Nov 25th, 2011, 11:21am:
But that's not an OTA ! An OTA has two high-impedance inputs ! |
Title: Re: Basic Curent Conveyor (CCII) operation Post by ssp on Nov 25th, 2011, 12:54pm Right.... but I guess that if the current source injects a very small current, let's say 1 nA, it can fit practically for both the requierements of OTA and the CCII ? This circuit comes from the following article and seems to work until the current source applied is 200 nA: Narula and al. A time-based VLSI potentiostat for ion current measurements:http://ieeexplore.ieee.org/search/freesrchabstract.jsp?tp=&arnumber=1608062&openedRefinements%3D*%26filter%3DAND%28NOT%284283010803%29%29%26searchField%3DSearch+All%26queryText%3Da+time-based+potentiostat They don't give the details about the operation of the CCII as they call it. |
Title: Re: Basic Curent Conveyor (CCII) operation Post by buddypoor on Nov 26th, 2011, 1:08am My only concern was the shown OTA symbol in connection with the term "CCII". If the shown circuit is able to work or not is another question I did not touch at all. (By the way: I have no chance to open the IEEE document). |
Title: Re: Basic Curent Conveyor (CCII) operation Post by Vladislav D on Dec 1st, 2011, 10:36am This circuit does not make sense. You confuse symbols of voltage and current sources |
Title: Re: Basic Curent Conveyor (CCII) operation Post by loose-electron on Dec 1st, 2011, 2:18pm Vladislav D wrote on Dec 1st, 2011, 10:36am:
Agreed - the circuit as drawn needs to be fixed. Please give a better description of what you are trying to do or trying to understand. You got a current source with a ground at each end. Does not compute! :) |
Title: Re: Basic Curent Conveyor (CCII) operation Post by RobG on Dec 1st, 2011, 6:56pm ssp wrote on Nov 25th, 2011, 12:54pm:
No, the size of the current doesn't matter - the input stages are completely different by definition. |
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