Tunable constant current source with temperature and power supply compensation

A tunable constant current source having temperature and power supply compensation, said tunable constant current source comprising:

• a voltage regulator operable to provide a substantially constant bias voltage Vb, said voltage regulator includes a gross temperature compensation circuit operable to switch between one of a plurality of branches depending upon an operating temperature of a circuit employing said tunable constant current source to maintain said bias voltage VB substantially constant;
• a differential amplifier operable to receive said bias voltage VB and maintain a load voltage VL substantially equal to said bias voltage VB by way of a negative feedback;
• a current source operable to generate a substantially constant current IREF from said differential amplifier;
• and
• a compensating load operable to vary with temperature changes to maintain said current IREF substantially constant, wherein said tunable constant current source may operate in a supply voltage range between about 0.5 volts to about 1.8 volts.