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Measurements >> Other Measurements >> Giving an input DC bias current for an IC
https://designers-guide.org/forum/YaBB.pl?num=1496280320

Message started by Venky_analog on May 31^st, 2017, 6:25pm

Title: Giving an input DC bias current for an IC
Post by Venky_analog on May 31^st, 2017, 6:25pm

Hi,

I am trying to give the DC bias current to an IC from an external source. The way I am generating this current is by using a potentiometer structure shown below.

By changing both VDD (tunable) and R1 (potentiometer), I can change the current. The VDD comes from an LDO and hence it's kind of accurate.

The thing is I placed another series resistor R2 to reduce the variations in the current due to possible variations in the potentiometer, as I heard potentiometers are very sensitive to their environments and tend to change with time a lot.

My quesiton is if I keep R2 like 25% of R1, would it be good enough? Also, is this a good way of generating current externally for biasing circuits inside an IC?

Thanks in advance

Title: Re: Giving an input DC bias current for an IC
Post by kabir_fakir on Aug 30^th, 2017, 4:50am

For me it looks fine. I am only concerned about the thermal noise of the resistor itself as you are introducing 2 rsistors
As I did testing with my IC too. to generate the dc current, I took a clean power supply (Agilent- E3644A) and put a huge resistor (in 10k range) in series with that (instead of potentiometer ). And then I keep varying the DC power supply as per requirement of the current.