Apparatus and method for duplicating currents

A current duplicator for receiving a calibration current and providing an output current to a load, comprising:

• a buffer, having an input and an output, for converting a difference current into a buffered difference current, said difference current equal to the difference between the output current and the calibration current;
• a transconductor having an input with a parasitic capacitance for storing a differential voltage during a supply time period and for converting said buffered difference current into said voltage during a feedback time period, said transconductor for converting said voltage into the output current and providing the output current at an output;
• and
• a first set of switches for coupling the output current to the load during said supply time, the output current remaining within a predetermined deviation from the calibration current during said supply time;
• and
• a second set of switches for feeding back said buffered difference current to said input during said feedback period at least until the output current becomes substantially equal to the calibration current.

A digital-to-analog converter comprising:

• a bank of current duplicators, each for providing an output current during a supply period, for providing a total output current to a load in response to a digital input signal;
• a spare duplicator for supplying an output current in place of a current duplicator during a calibration period of said current duplicator, each current duplicator and said spare duplicator comprising,
• a transconductor having a differentially coupled input with a parasitic capacitance for storing a voltage during a supply period and for converting a difference current into said voltage during a feedback period, said difference current equal to the difference between the output current and said calibration current, said transconductor for converting said voltage into the output current and providing the output current at an output,
• a first switch set for coupling the output current to the load during said supply period, the output current remaining within a predetermined amount from said calibration current during said supply period and
• a second switch set for feeding back said difference current to said input during said feedback period at least until the output current becomes substantially equal to a calibration current.

A method for providing to a load an output current substantially equal to a reference current comprising the steps of:

• generating a difference current equal to the difference between the output current and the reference current during a feedback period;
• converting said difference current into a differential voltage until said difference current substantially equals zero;
• storing said differential voltage during a supply period;
• converting said differential voltage into the output current;
• and
• providing the output current to the load during said supply period, the output current remains substantially within a range from said reference current.

A method for providing to a load an output current substantially equal to a reference current comprising the steps of:

• (a) generating a difference current equal to the difference between the output current and the reference current;
• (b) generating a buffered difference current from said difference current;
• (c) converting said buffered difference current into a voltage during a calibration period until the output current becomes substantially equal to the reference current;
• (d) storing said voltage during a supply period;
• (e) converting said voltage into the output current;
• and
• (f) providing the output current to the load during the supply period, the output current remains substantially within a range from the reference current.

An analog-to-digital converter for converting a voltage into a digital data form, the analog-to-digital converter comprising:

• a single-end-to-differential converter for converting the voltage to a differential voltage;
• a sample and hold circuit for generating a differential sample voltage by sampling the differential voltage during a sample period and for holding the differential sample voltage and converting the differential sample voltage into a sample current during a conversion period, said sample and hold circuit comprising,
• a switch network for sampling said differential voltage,
• a transconductor having a differentially coupled input with a parasitic capacitance for receiving said differential voltage during said sampling period and storing said differential voltage during said conversion period, said transconductor for converting said differential voltage into said sample current.