Three-state buffer circuit

A resettable track and hold circuit, comprising:

• a three-state buffer circuit, the three state buffer circuit comprising a voltage follower for directly driving a sampling capacitor at an output terminal of the three-state buffer circuit, and a switched capacitor circuit connected at an input of the voltage follower and configured to control the voltage follower to operate in one of:
• a tracking state, at which the voltage follower is configured to provide an output voltage at the output terminal at a level corresponding to an input voltage at an input terminal of the three-state buffer circuit;
• a hold state, at which the voltage follower is configured not to provide any output voltage at the output terminal;
• and
• a reset state at which the voltage follower is configured to provide an output voltage at the output terminal at a reset voltage;
• and
• a sampling capacitor connected in parallel between the output terminal of the three-state buffer circuit and an output terminal of the resettable track and hold circuit thereby providing the output voltage of the three-state buffer circuit across the sampling capacitor.

An apparatus, comprising an analog to digital converter, ADC, the ADC comprising a resettable track and hold circuit, the resettable track and hold circuit comprising:

• a three-state buffer circuit, the three state buffer circuit comprising a voltage follower for directly driving a sampling capacitor at an output terminal of the three-state buffer circuit, and a switched capacitor circuit connected at an input of the voltage follower and configured to control the voltage follower to operate in one of:
• a tracking state, at which the voltage follower is configured to provide an output voltage at the output terminal at a level corresponding to an input voltage at an input terminal of the three-state buffer circuit;
• a hold state, at which the voltage follower is configured not to provide any output voltage at the output terminal;
• and
• a reset state at which the voltage follower is configured to provide an output voltage at the output terminal at a reset voltage;
• and
• a sampling capacitor connected in parallel between the output terminal of the three-state buffer circuit and an output terminal of the resettable track and hold circuit thereby providing the output voltage of the three-state buffer circuit across the sampling capacitor.