Prev: EPE Mag July 1998
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From: Michael Robinson on 13 May 2010 19:28
I was reading this article

http://electronicdesign.com/article/power/design-a-differential-voltage-controlled-current-s.aspx

and looking at the accompanying diagram

http://archive.electronicdesign.com/files/29/11878/figure_02.gif

The diagram shows a current of iD1 flowing into the X terminal of the upper
current conveyor and an equal current iD1 flowing to the YZ node from below.
I think as drawn, that current would actually be 2iD1, because the currrent
at X is reflected to Y and to Z both, adding up to 2X at the node. Shouldn't
the Z terminal of the upper current conveyor be left open or connected to
one of the supplies instead of connecting to Y?


From: John Larkin on 13 May 2010 22:22
On Thu, 13 May 2010 19:28:35 -0400, "Michael Robinson"
<nospam(a)billburg.com> wrote:

>I was reading this article
>
>http://electronicdesign.com/article/power/design-a-differential-voltage-controlled-current-s.aspx
>
>and looking at the accompanying diagram
>
>http://archive.electronicdesign.com/files/29/11878/figure_02.gif
>
>The diagram shows a current of iD1 flowing into the X terminal of the upper
>current conveyor and an equal current iD1 flowing to the YZ node from below.
>I think as drawn, that current would actually be 2iD1, because the currrent
>at X is reflected to Y and to Z both, adding up to 2X at the node. Shouldn't
>the Z terminal of the upper current conveyor be left open or connected to
>one of the supplies instead of connecting to Y?
>

I googled "current conveyor" and the first hit was this:

http://www.maxim-ic.com/app-notes/index.mvp/id/4198

but it looks to me like Fig 1 is wrong.

I assume the 3-terminal current sources are mirrors. This looks a lot
like a current-mode opamp.

John

From: Jim Thompson on 13 May 2010 22:53
On Thu, 13 May 2010 19:22:48 -0700, John Larkin
<jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote:

>On Thu, 13 May 2010 19:28:35 -0400, "Michael Robinson"
><nospam(a)billburg.com> wrote:
>
>>I was reading this article
>>
>>http://electronicdesign.com/article/power/design-a-differential-voltage-controlled-current-s.aspx
>>
>>and looking at the accompanying diagram
>>
>>http://archive.electronicdesign.com/files/29/11878/figure_02.gif
>>
>>The diagram shows a current of iD1 flowing into the X terminal of the upper
>>current conveyor and an equal current iD1 flowing to the YZ node from below.
>>I think as drawn, that current would actually be 2iD1, because the currrent
>>at X is reflected to Y and to Z both, adding up to 2X at the node. Shouldn't
>>the Z terminal of the upper current conveyor be left open or connected to
>>one of the supplies instead of connecting to Y?
>>
>
>I googled "current conveyor" and the first hit was this:
>
>http://www.maxim-ic.com/app-notes/index.mvp/id/4198
>
>but it looks to me like Fig 1 is wrong.

Yep, "Dot" in the wrong place.

>
>I assume the 3-terminal current sources are mirrors. This looks a lot
>like a current-mode opamp.
>
>John

Yep :-)

...Jim Thompson
--
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Prev: EPE Mag July 1998
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