Importance

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Abstract

An analog oscillator for an integrated circuit operates at low frequency with reduced sensitivity to noise and can be implemented with a capacitor that takes up a small amount of die space. The oscillator charges a capacitor by generating a current with a charge current source and then shunting a portion of the current away from the capacitor with a shunt current source. The current sources are implemented in bipolar transistors which are operated at high current to reduce sensitivity to noise. The capacitor is charged slowly by a small difference current which is equal to the difference between the current from the charge current source and the current from the shunt current source. A Schmitt trigger comparator compares the capacitor voltage to a reference voltage and controls a discharge current source which discharges the capacitor. The current sources include current mirrors and are temperature compensated.

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First Claim