Precision oscillator circuits and methods with switched capacitor frequency control and frequency-setting resistor
First Claim
1. 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 with a frequency-setting resistor, the method comprising:
- generating a current through the frequency-setting resistor;
coupling the voltage across the frequency-setting resistor to a first input of the integrating amplifier circuit;
copying the current to a second input of the integrating amplifier circuit using a controllable current source;
generating a ramped output waveform with the integrating amplifier circuit based on the current at the second input of the integrating amplifier circuit;
generating discrete changes in the ramped output waveform using a first switched capacitor coupled to the second input of the integrating amplifier circuit, to provide the oscillating waveform with a frequency based 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 integrating amplifier circuit using switches substantially controlled by the oscillating waveform.
3 Assignments
0 Petitions
Accused Products
Abstract
A precision oscillator circuit providing a periodic waveform is provided. A periodic waveform is provided by the use of an integrating op-amp circuit in conjunction with a switched capacitor frequency control loop and a user input adapted to be coupled with a frequency-setting resistor. The frequency of the periodic waveform is determined by the values of the switched capacitor and the resistor. The oscillator circuit has an arrangement which minimizes the effect of the op-amp circuit'"'"'s offset voltage. The user input is kept robust against user-introduced capacitance by the use of controllable current sources to bias the op-amp circuit. A linearity correction circuit is also provided to correct for non-ideal op-amp circuits.
62 Citations
18 Claims
-
1. 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 with a frequency-setting resistor, the method comprising:
-
generating a current through the frequency-setting resistor;
coupling the voltage across the frequency-setting resistor to a first input of the integrating amplifier circuit;
copying the current to a second input of the integrating amplifier circuit using a controllable current source;
generating a ramped output waveform with the integrating amplifier circuit based on the current at the second input of the integrating amplifier circuit;
generating discrete changes in the ramped output waveform using a first switched capacitor coupled to the second input of the integrating amplifier circuit, to provide the oscillating waveform with a frequency based 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 integrating amplifier circuit using switches substantially controlled by the oscillating waveform. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
-
9. 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 power supply through a frequency-setting resistor;
a first switched capacitor coupled to a second input of the amplifier circuit;
a plurality of switches that is coupled to the first switched capacitor that controls the coupling of the first switched capacitor to the integrating amplifier circuit, and wherein the plurality of switches is substantially controlled by the output waveform; and
a first controllable current source coupled to the frequency-setting resistor and to the switched capacitor circuit, wherein the current source provides a current to the second input that is proportional to the current through the frequency-setting resistor. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
-
-
18. 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 with a frequency-setting resistor, the method comprising:
-
generating a current through the frequency-setting resistor;
coupling the voltage across the frequency-setting resistor to a first input of the integrating amplifier circuit;
generating a second current to a second input of the integrating amplifier circuit using a controllable current source, the second current being proportional to the first current;
generating a ramped output waveform with the integrating amplifier circuit based on the current at the second input of the integrating amplifier circuit;
generating discrete changes in the ramped output waveform using a first switched capacitor coupled to the second input of the integrating amplifier circuit, to provide the oscillating waveform with a frequency based 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;
controlling the coupling of the switched capacitor with the integrating amplifier circuit using switches substantially controlled by the oscillating waveform;
converting the output waveform using a sample-hold circuit to provide a sampled and held output; and
controlling a voltage controlled oscillator to provide the oscillating waveform based on sampled and held output.
-
Specification