Single supplier digital controlled current source ?

Daar,

I'm looking for a programmable current source like the on in Fig 3. In CN0151 but than working on a single power supplier.

For my application I can live with a possible, but accurate output current offset.

Looking forward to receive some reactions,

Greetings Patrick

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  • Hi Patrick,

    I apologize for the delayed reply. I have two options for you, both will work in a single supply configuration.

    Given the resolution that you want of 100nA, it would definitely not be advisable to use the circuit in figure 3 of CN-0151. The resistors of 15kohm and 150kohm alone would give you a fair amount of inaccuracy. I think that the circuit in CN-0099 would work better for your application. This mainly uses a diff amp, particularly the AD8276, to obtain a constant current out of the circuit. Other than being able to use the circuit in a single supply configuration, the ICs are small in size so you end up using only a small board size. You can refer to the following link to get additional information on designing your current source.

    Another option would be to use the newer AD8420 in the following configuration:

    The main sources of error out of this circuit would be the AD8420's bias current, offset, and CMRR, all of which should be small enough to still be able to achieve a resolution of 100nA.

    Since you want a digitally programmable circuit, you could interface these with the AD5060 or the AD5660. Both are 16-bit DACs, which will suffice for your requirement.

    I hope this helps!

    Kris

Reply
  • Hi Patrick,

    I apologize for the delayed reply. I have two options for you, both will work in a single supply configuration.

    Given the resolution that you want of 100nA, it would definitely not be advisable to use the circuit in figure 3 of CN-0151. The resistors of 15kohm and 150kohm alone would give you a fair amount of inaccuracy. I think that the circuit in CN-0099 would work better for your application. This mainly uses a diff amp, particularly the AD8276, to obtain a constant current out of the circuit. Other than being able to use the circuit in a single supply configuration, the ICs are small in size so you end up using only a small board size. You can refer to the following link to get additional information on designing your current source.

    Another option would be to use the newer AD8420 in the following configuration:

    The main sources of error out of this circuit would be the AD8420's bias current, offset, and CMRR, all of which should be small enough to still be able to achieve a resolution of 100nA.

    Since you want a digitally programmable circuit, you could interface these with the AD5060 or the AD5660. Both are 16-bit DACs, which will suffice for your requirement.

    I hope this helps!

    Kris

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