hi, i would like to habe current from 3 bit . the first bit 40 microA, second bit 20microA and the last bit 10microA. Attached is my circuit design but i am unable to get the current as required. Any want able to help?
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).
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.
E
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.
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.