Patent ID: 6326859
Filing Date: 2001-12-04
Classification: H03K

Abstract:
An oscillator circuit, comprising:a current supply circuit, for generating a reference current;a capacitor array, comprising a plurality of capacitors and switches for switching the capacitors into and out of the circuit to control a total trimming capacitance value; anda timing circuit, connected to the capacitor array to receive a voltage across the capacitor array as an input thereto;wherein the reference current is supplied to the capacitor array at respective first nodes of the plurality of capacitors to charge or discharge the capacitors switched into the circuit, and the timing circuit produces an output signal with a period which depends on the time taken for the voltage across the capacitor array to reach one or more voltage threshold values;further comprising:an operational amplifier, having a first input terminal connected to a reference voltage, a second input terminal connected to the respective first nodes of the capacitors in the capacitor array, and an output terminal connected between the capacitor array and the timing circuit, such that the capacitor array forms a feedback loop around the operational amplifier, and such that the respective first nodes of the capacitors are held at a relatively constant voltage.