Flipped gate current reference and method of using

A current reference comprising:

• a control resistor;
• a tracking voltage generator comprising:
• a first transistor having a first size and a flipped gate;
• and
• a second transistor having a second size;
• wherein the tracking voltage generator is configured to provide, at an output node, a tracking voltage having a temperature dependency over a temperature range based on a ratio of the second size to the first size, the temperature dependency of the tracking voltage thereby being substantially equal to a temperature dependency of the control resistor over the temperature range;
• a third transistor coupled between the output node and ground, the third transistor being configured so that a voltage drop across the third transistor is substantially the same as a voltage drop across the second transistor which compensates for an effect on the tracking voltage;
• and
• an amplifier circuit configured to receive the tracking voltage and maintain a first voltage at a first terminal of the control resistor, the first voltage being substantially equal to the tracking voltage;
• and
• a current mirror configured to receive a reference current based on a resistance of the control resistor and generate a mirrored current from the reference current,
• the current reference thereby being configured to maintain the mirrored current at a constant value over the temperature range.

A method of operating a current reference, the method comprising:

• for an amplifier coupled to a first node, receiving a tracking voltage with the amplifier on the first node;
• maintaining, using the amplifier, a reference current through a control resistor;
• for first, second and third transistors coupled to the first node, the third transistor being coupled between the first node and ground, and the third transistor being configured so that a voltage drop across the third transistor is substantially similar to a voltage drop across the second transistor,
• generating the tracking voltage at the first node, the first transistor having a first size and a flipped gate, and the second transistor having a second size, the tracking voltage being based on a ratio of the second size to the first size;
• and
• for a channel leakage component of current through the second transistor, shunting the channel leakage component using the third transistor to compensate an effect on the tracking voltage;
• and
• wherein the tracking voltage has a first temperature dependency over a temperature range which is substantially equal to a second temperature dependency over the temperature range of a resistance of the control resistor, the reference current thereby being maintained at a constant value over the temperature range.