Radiation hardened by design CMOS crystal oscillator for readout telemetry

A method of generating a clock signal using a comparator having a positive comparator input, a negative comparator input, a proportional to absolute temperature (PTAT) PMOS bias input, a PTAT NMOS bias input, and a comparator output, the method comprising:

• coupling a resonator element and series resistor between the comparator output and the negative comparator input to generate a clock signal at the comparator output;
• and
• a feedback resistor between the comparator output and the comparator negative input to provide a DC path for linearizing gain of the comparator;
• and
• coupling a PTAT bias circuit to the PTAT PMOS bias input and the PTAT NMOS bias input, the PTAT bias circuit configured to drive the PTAT PMOS bias input and the PTAT NMOS bias input to maintain an approximately constant gain and frequency of the clock signal over an operating temperature range of the clock source.