I'm building an oscillator for a battery powered capacitive position sensor and I need it to have a high swing (>800 mV) at the output while keeping power consumption low enough. I'm feeding the output into the FPGA LVDS input so the oscillator must have a sufficient swing to drive it. Also it has to have large tuning range, a high ΔF/ΔC ratio and one side of the sensor must be grounded.
Right now I'm using a cascode Lampkin oscillator (see picture below), it has quite high sensitivity but it outputs only up to 600 mV into 4 pF load, consuming 2 mA at 3.3V. I recently built a cross-coupled class D oscillator and I got 3 times Vcc at the output while consuming only 1.2 mA! But it's a differential oscillator so I can't use it because the probe is not differential and it can't handle the whole possible capacitance range. I also saw a class-C Hartley oscillator that has higher efficiency by the looks of it but I don't quite understand how it works and how to change the circuit for my application.
So is there any oscillator topologies that are more power efficient than the one I'm using and still sensitive enough to capacitance changes?
