Self-biasing integrated oscillator without bandgap reference

An integrated oscillator comprising:

• an R-S flipflop;
• a first and a second capacitor;
• a first current source transistor having a drain and a gate;
• a first and a second current-steering transistor, each having a source coupled to the drain of the first current source transistor, a drain of the first current-steering transistor coupled to the first capacitor, and a drain of the second current-steering transistor coupled to the second capacitor, the first current-steering transistor having a gate coupled to a first output of the R-S flipflop, and the second current-steering transistor having a gate coupled to a second output of the R-S flipflop;
• a first sense inverter having input coupled to the first capacitor, the first sense inverter being powered by a feedback circuit adapted to sense voltages on the first and second capacitor;
• and
• a second sense inverter having input coupled to the second capacitor and powered by the feedback circuit;
• wherein the R-S flipflop has a first input coupled to an output of the first sense inverter and a second input coupled to an output of the second sense inverter;
• and
• wherein the feedback circuit comprises a first differential amplifier having an inverting and a noninverting input, the inverting input coupled through a first resistor to the first capacitor and through a second resistor to the second capacitor, and a third capacitor coupled between the inverting input and an output of the differential amplifier.

A method of generating a signal comprising:

• generating a first controlled current;
• switching the first controlled current onto a selected capacitor, the selected capacitor selected from the group consisting of a first capacitor and a second capacitor according to at least one output of an R-S flipflop;
• detecting a voltage on the first capacitor reaching an oscillator threshold voltage and switching a state of the R-S flipflop;
• and
• detecting a voltage on the second capacitor reaching the oscillator threshold voltage and switching the state of the R-S flipflop;
• wherein the oscillator threshold voltage is a threshold voltage of a reference inverter comprising an N type transistor having source coupled to ground, gate coupled to input of the inverter, and drain coupled to output of the inverter, a P type transistor having source coupled to a control voltage, gate coupled to an input of the inverter, and drain coupled to the output of the inverter.