Thanks for your help. ;) Somehow, I face another problem dealing with my TC9400 :-\. It is a frequency to voltage IC from MICROCHIP. I had inputed the frequency supply at pin 11, and the result get at pin12 is very low. The frequency input is 4k, 10k, 20k, 40k; I get more or less around 1.23v. Is the diagram wrong? Thanks.