RELAXATION OSCILLATOR WITH LOW DRIFT AND NATIVE OFFSET CANCELLATION

摘要

Relaxation oscillator circuitry is presented with low drift and native offset cancellation, including an amplifier amplifying a first current signal to provide a pulse amplifier output waveform, an integrator integrating a second current signal to provide a ramp output waveform, and a comparator comparing the integrator output waveform with a threshold set by the amplifier output waveform to generate an alternating oscillator output used to switch the polarities of the first and second current signals.

主权项

1. An oscillator circuit, comprising:
an amplifier circuit comprising: a first amplifier including a first input coupled with a bias node, a second input coupled with a first node, and a first amplifier output providing a first amplifier output signal; and a resistance coupled between the first node and the first amplifier output; an integrator circuit, comprising: a second amplifier including a first input coupled with the bias node, a second input coupled with a second node, and a second amplifier output providing a second amplifier output signal; and a capacitance coupled between the second node and the second amplifier output; a comparator comprising: a first comparator input coupled with the first amplifier output to receive the first amplifier output signal, a second comparator input coupled with the second amplifier output to receive the second amplifier output signal, and a comparator output providing an oscillator output signal alternating between a first level and a different second level; a first current source providing a first current signal of a first current value to the first node; a second current source providing a second current signal of the first current value to the second node; a third current source providing a third current signal of twice the first current value from a third node to a constant voltage node; a fourth current source providing a fourth current signal of twice the first current value from a fourth node to the constant voltage node; and a switching circuit operative according to the oscillator output signal to disconnect the third node from the first node and to disconnect the fourth node from the second node when the oscillator output signal is at the first level, and to couple the third node with the first node and to couple the fourth node with the second node when the oscillator output signal is at the second level.