deniz88
Member level 2
Hi,
i want to make a digitally(FPGA) controlled negative current source. C1 capacitor is the load.
- i want that current change equally for every single bit , for istance
1110 = Ix
1101 = 2Ix
1100 = 3Ix...
but in my circuit current doesnt change propartional. i arrange resistor values to make it 2Ix but this time 3Ix doesnt happen.
-another issue is, i am getting current peaks on fpga pin, is it because i connected it to negative current source(i had to do it to make sure Q7 base current flows)? I also tried Ref voltage to Q7 collector but after that i couldnt control current at all.
any suggestion to prevent these peaks, or any other sugestions to implement this circuit?
thanks a lot for helps.
i want to make a digitally(FPGA) controlled negative current source. C1 capacitor is the load.
- i want that current change equally for every single bit , for istance
1110 = Ix
1101 = 2Ix
1100 = 3Ix...
but in my circuit current doesnt change propartional. i arrange resistor values to make it 2Ix but this time 3Ix doesnt happen.
-another issue is, i am getting current peaks on fpga pin, is it because i connected it to negative current source(i had to do it to make sure Q7 base current flows)? I also tried Ref voltage to Q7 collector but after that i couldnt control current at all.
any suggestion to prevent these peaks, or any other sugestions to implement this circuit?
thanks a lot for helps.