Looking for a colpits oscillator based upon either an OP-amp or comparitor. The circuit already uses a window comparitor so there are two left over in the package. The circuit is a basic position indicator with a variable inductor input to a colpits oscillator feeding a V-F converter to the window comparitor. A dual green/red LED provides the output.
Thanks.
The frequency does not matter much. The inductor core will change from zero to full position in about a second. The position varies with operating conditions.
The range of frequency is whatever can be detected by a LM2907. The output voltage of this goes through a potentiometer to the window comparitor to set the high range limit. A potentiometer in the window circuit sets the low range limit.
I have seen a simple circuit that uses a single inverter gate with the inductor between the input and output and a capacitor from input and output to ground. However that requires an additional chip. I need to keep the parts at a minimum.
The LM3900 is not a comparator or even an op amp; it is an amplifier with a current mirror input. It may work in your application, but you have to know how to use it.