I wanted to ask all of you LFO experts about the values that are chosen for the voltage divider.
I have seen several LFO circuits, many of which look very similar, that use various values for the divider network. Some use two 10K resistors, others use two 220K, and still others use two 680K (one to 9v, the other to ground and the Vref is picked off from the two resistors that are joined together). Basically, in a nutshell, I have seen many different values used.
My questions revolves around the Vref. If two equal value resistors are used as a voltage divider to get approximately 4.5 volts for Vref, why are so many different values used for these two resistors? Could you use a set value, say 100K, or is there some current limiting going on here as well (the reason for the use of other values) for the op amp?
Just wondering about this. I guess my question is really, is it critical for the different values depending on the op amp used or is it just what ever the designer had on hand to use for the Vref voltage?
Thanks guys!
Jim
Using equal values for a divider will always give you exactly 1/2 of the supply voltage. The difference between the higher and lower values of resistors is the current output.
i believe, in this case, the value of the resistors is not critical. they just can't be "too low" or "too high". typically greater than 10k but less than 500K. in some high impedance applications, for example some MOSFETs circuits, higher values may be okay.