Hey all-
I am having problems using a JFET as a variable resistor. For one, the information on the subject is vague. I'd like to see if anyone could give some advice on using the datasheets to find the useful resistance range, i.e. Rmin to Rmax.
The problem I am having is with the JFET tolerances. My circuit works, and works extremely well, however, 33% of JFETs don't measure to the spec I need (too high or too low R min). How do I work around this problem, especially since this is an all SMD design?
Maybe someone with manufacturing experience could help. Could I buy JFETs tested at the factory? Can you test before or during assembly and have the "bad" parts kicked out of the placement machines, or do you just have to test the whole assembly and pitch it if it doesn't test well? It would seem like this is a common problem with JFETs and I'm not the first person trying to overcome this.
Thank you in advance for your help.
I am having problems using a JFET as a variable resistor. For one, the information on the subject is vague. I'd like to see if anyone could give some advice on using the datasheets to find the useful resistance range, i.e. Rmin to Rmax.
The problem I am having is with the JFET tolerances. My circuit works, and works extremely well, however, 33% of JFETs don't measure to the spec I need (too high or too low R min). How do I work around this problem, especially since this is an all SMD design?
Maybe someone with manufacturing experience could help. Could I buy JFETs tested at the factory? Can you test before or during assembly and have the "bad" parts kicked out of the placement machines, or do you just have to test the whole assembly and pitch it if it doesn't test well? It would seem like this is a common problem with JFETs and I'm not the first person trying to overcome this.
Thank you in advance for your help.