3 Replies Latest reply on Mar 29, 2020 7:38 PM by ArM_1088156

    Current source with IDAC8


      I want a current source to test one of my trans-impedance amplifiers.


      My requirement is to generate a dc current source whose value varies between 0.1 nA to 1 nA, if possible up to 1.5 nA.


      I hope I can do it with the IDAC8 module and few resistors with the current division principle.


      Though I have a few questions regarding this.


      1. I'm not able to generate 0.125 uA with software mode (through a program), even though I can do it in hardware mode. Since the IDAC_SetValue function supports only unsigned integers. Is there any way to generate 0.125 uA current with software. After all, I'll control the current source with the help of a LabView program or through a Windows hyper terminal application.


      2. I generated a=1 uA current flowing out of the port pin P 0(6) with the IDAC module. I connected a 100 kohm resistor between the pin P 0(6) and PSoC ground and measured the voltage between the 100 kohm resistor. I sourced 1 uA and measured the voltage and seems to be ok with the calculated value.  But, when the measured value is supposed to be more than 3.3 V (PSoC in 3.3V mode), I repeatedly measure the voltage to be only 3.3 V as maximum value even the supposed measured value to be more than 5 V or so. Why is it so?


      Kindly suggest answers.