An apparatus for providing a voltage reference, comprising: - a Zener diode circuit (110, 116; 210), coupled between a first supply terminal (112; 232) and a second supply terminal (114; 234), to provide a first input reference voltage level, wherein the Zener diode circuit (110, 116; 210) has a positive temperature coefficient; - a voltage reduction circuit (120; 216a, 216b) to provide a second input reference voltage level that tracks the first input reference voltage level; and - a proportional-to-absolute temperature, PTAT, circuit (130; 230) includes a differential circuit having first and second differential paths (235a, 235b), wherein: the first differential path is configured to provide an output drive current and an output reference voltage at an output node (140; 240) of the PTAT circuit; the second differential path is configured to provide an output reference voltage at the output node of the PTAT circuit; the first differential path includes a first bipolar transistor to pass current between the first supply terminal and the second supply terminal, the first bipolar transistor having a control terminal driven in response to the second input reference voltage level, the first bipolar transistor also having an emitter terminal; the PTAT circuit having a feedforward path from a collector of the first bipolar transistor to the output node; the second differential path includes a second bipolar transistor to pass current between the first supply terminal and the second supply terminal, the second bipolar transistor having a control terminal driven in response to the output reference voltage at the output node, the second bipolar transistor also having an emitter terminal that is connected to the emitter terminal of the first bipolar transistor; such that the PTAT circuit (130; 230) is configured to provide a level of temperature compensation that is set by a ratio of current density of the first bipolar transistor and the second bipolar transistor. - a Zener diode circuit (110, 116; 210), coupled between a first supply terminal (112; 232) and a second supply terminal (114; 234), to provide a first input reference voltage level, wherein the Zener diode circuit (110, 116; 210) has a positive temperature coefficient; - a voltage reduction circuit (120; 216a, 216b) to provide a second input reference voltage level that tracks the first input reference voltage level; and - a proportional-to-absolute temperature, PTAT, circuit (130; 230) includes a differential circuit having first and second differential paths (235a, 235b), wherein: the first differential path is configured to provide an output drive current and an output reference voltage at an output node (140; 240) of the PTAT circuit; the second differential path is configured to provide an output reference voltage at the output node of the PTAT circuit; the first differential path includes a first bipolar transistor to pass current between the first supply terminal and the second supply terminal, the first bipolar transistor having a control terminal driven in response to the second input reference voltage level, the first bipolar transistor also having an emitter terminal; the PTAT circuit having a feedforward path from a collector of the first bipolar transistor to the output node; the second differential path includes a second bipolar transistor to pass current between the first supply terminal and the second supply terminal, the second bipolar transistor having a control terminal driven in response to the output reference voltage at the output node, the second bipolar transistor also having an emitter terminal that is connected to the emitter terminal of the first bipolar transistor; such that the PTAT circuit (130; 230) is configured to provide a level of temperature compensation that is set by a ratio of current density of the first bipolar transistor and the second bipolar transistor. the first differential path is configured to provide an output drive current and an output reference voltage at an output node (140; 240) of the PTAT circuit; the second differential path is configured to provide an output reference voltage at the output node of the PTAT circuit; the first differential path includes a first bipolar transistor to pass current between the first supply terminal and the second supply terminal, the first bipolar transistor having a control terminal driven in response to the second input reference voltage level, the first bipolar transistor also having an emitter terminal; the PTAT circuit having a feedforward path from a collector of the first bipolar transistor to the output node; the second differential path includes a second bipolar transistor to pass current between the first supply terminal and the second supply terminal, the second bipolar transistor having a control terminal driven in response to the output reference voltage at the output node, the second bipolar transistor also having an emitter terminal that is connected to the emitter terminal of the first bipolar transistor; such that