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Unable to get current

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ericgibbs

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hi
I get missing models errors with the asc files.
This image shows that the VOUT label is NOT connected.
E
 

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ericgibbs

Well-Known Member
Most Helpful Member
hi 36,
I have tried again, downloaded all your files, still cannot get it to open, missing model error.

Look a this image, move the VOUT label on your circuit so it is the same as image, else it is NOT connected.

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spec

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Most Helpful Member
Hi momo,

What DAC are you using?

If you want to sum currents and produce a corresponding voltage out put (so that you can measure the total current), the usual way is to use a current-summing, virtual-earth amplifier (transimpedance amplifier). The transfer function is Vout = -Iin* R23.

UPDATE: The current inputs to the circuit below are the current outputs from the DACs (should be 3 not 4 as shown).


2016_11_05_Iss1_ETO_CURRENT_SUMMING_AMP_VER1.png


 
Last edited:

ericgibbs

Well-Known Member
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hi 36,
I have combined and redrawn your asc file, it now runs for me.
Is the image showing the result you are expecting.?
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momo36

New Member
hi ericgibbs,

thanks for ur help. i would like to have current where bit 1 40micro second bit 20 micro and third bit 10 micro
 

ericgibbs

Well-Known Member
Most Helpful Member
hi ericgibbs,
thanks for ur help. i would like to have current where bit 1 40micro second bit 20 micro and third bit 10 micro
Hi,
Do you mean like this plot.?
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momo36

New Member
i mean bit one has current of 40 microA, bit 2 has current of 20 micro A and bit 3 has current of 10 micro ampere
 

ericgibbs

Well-Known Member
Most Helpful Member
thanks for ur help. i would like to have current where bit 1 40micro second bit 20 micro and third bit 10 micro
hi,
You did say 40micro second.
I will look at the problem later.

You may find this option for setting the Bits useful for testing, Set the Bits by using the SW SET = 1 or 0

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ericgibbs

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hi,
Which node/component of the circuit are you wanting to measure the current thru.?
 

ericgibbs

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Most Helpful Member
i wanted to measure the Iout current for bit 1 bit 2 and bit 3
hi,
You have 3 identical circuits, as drawn each circuit is able to source a current of ~ 50uA
The only parameter that will change with different Bit patterns is Vout.

Is this a College assignment or an actual circuit you are designing.
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eTech

Well-Known Member
Hi

Mouse over each output wire (the cursor will change to a current probe icon), then press ALT-Click.
The measurement will display in the waveform pane.

Or

You can use a voltage source as a current meter. Place it in series with each output wire and set its value to zero.
Then mouse over the voltage source and click. The measurement will display in the waveform pane

I changed the trans time to 10uS. I also dded wire labels to example B for clarity.

See attached.
 

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Last edited:

eTech

Well-Known Member
hi
I get missing models errors with the asc files.
This image shows that the VOUT label is NOT connected.
E
Open the Switchable_Current_Source.asc file. Then from the Hierarchy menu, select "Open this sheets symbol".
The symbol will be auto created and placed in the current folder.
 

ericgibbs

Well-Known Member
Most Helpful Member
hi 36,
This is one option to get a 10uA,20uA,40uA current for 3 Bits.
Note I have labelled the Bit's MSB,Bit1,LSB.
E
 

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