Precision oscillator circuits and methods with switched capacitor frequency control and frequency-setting resistor

An oscillator circuit comprising an integrating amplifier circuit, the amplifier circuit that provides an output waveform, the oscillator circuit comprising:

• an independent current source that is coupled to provide a current to an input of the amplifier circuit;
• a switched capacitor circuit that is separated from the independent current source;
• and
• a plurality of switches, at least a portion of the plurality of switches being coupled to the switched capacitor circuit and the amplifier circuit, the plurality of switches that controls a coupling of the switched capacitor circuit to the amplifier circuit and wherein the plurality of switches is substantially controlled by the output waveform.

An oscillator circuit comprising an integrating amplifier circuit, the amplifier circuit that provides an output waveform, the oscillator circuit comprising:

• a first input of the amplifier circuit being adapted for coupling to a frequency-setting resistor through a source-drain channel of a FET;
• a switched capacitor coupled to the first input of the amplifier circuit;
• a plurality of switches, the plurality of switches being coupled to the switched capacitor and that controls the coupling of the switched capacitor to the amplifier circuit and wherein the plurality of switches is substantially controlled by the output waveform;
• a controllable voltage source coupled to a second input of the amplifier circuit, the controllable voltage source being adapted to provide a voltage to the second input proportional to a voltage across the frequency-setting resistor.

A method for generating a high-precision periodic oscillating waveform using an integrating amplifier circuit, the amplifier circuit having a first input adapted to be coupled through a Field Effect Transistor (FET) to a frequency-setting resistor and a second input, the method comprising:

• generating a first voltage across the frequency-setting resistor;
• generating a second voltage in proportion to the first voltage;
• coupling the second voltage to a second input of the amplifier circuit;
• generating a ramped output waveform using the amplifier circuit based at least in part on the second voltage;
• generating discrete changes in the ramped output waveform using a first switched capacitor coupled to the first input of the amplifier circuit to provide the oscillating waveform a frequency based at least in part on the values of the first switched capacitor and the frequency-setting resistor, the oscillating waveform having a substantially constant average value at a particular frequency;
• and
• controlling the coupling of the switched capacitor with the amplifier circuit using a plurality of switches substantially controlled by the oscillating waveform.

An oscillator circuit comprising an integrating amplifier circuit, the amplifier circuit that provides an output waveform, the oscillator circuit comprising:

• a first input of the amplifier circuit being adapted for periodic coupling to a frequency-setting resistor through a source-drain channel of a FET;
• a switched capacitor coupled to the first input of the amplifier circuit;
• a plurality of switches, the plurality of switches being coupled to the switched capacitor and that controls the coupling of the switched capacitor to the amplifier circuit and wherein the plurality of switches is substantially controlled by the output waveform;
• a controllable voltage source coupled to a second input of the amplifier circuit, the controllable voltage source being adapted to provide a voltage to the second input proportional to a voltage across the frequency-setting resistor.