A voltage reference circuit for receiving an input and producing an output reference voltage having a maximum value independent of a voltage of the input, the circuit comprising: an input for receiving the input voltage; a first current controlling element which allows current to flow as an increasing, non-linear function of voltage at least within a first range of voltages; a capacitance connected to the input via the first current controlling element; a second current controlling element which allows current to flow as an increasing, non-linear function of voltage at least within a second range of voltages; and an output at which the output reference voltage is produced, wherein the first current controlling element and the second current controlling element are connected in series between the input and a common reference, with the second current controlling element between the first current controlling element and the common reference, the output comprises a node between the two current controlling elements, the first and second range of voltages overlap and the second current controlling element is configured to vary the function by which it allows current to flow in dependence on the input voltage; the voltage reference circuit characterised by comprising: a reset input for receiving a reset input; and a third current controlling element connected in series between the first current controlling element and the output, wherein the third current controlling element is configured to allow current to flow in dependence on a voltage received at the reset input. an input for receiving the input voltage; a first current controlling element which allows current to flow as an increasing, non-linear function of voltage at least within a first range of voltages; a capacitance connected to the input via the first current controlling element; a second current controlling element which allows current to flow as an increasing, non-linear function of voltage at least within a second range of voltages; and an output at which the output reference voltage is produced, wherein the first current controlling element and the second current controlling element are connected in series between the input and a common reference, with the second current controlling element between the first current controlling element and the common reference, the output comprises a node between the two current controlling elements, the first and second range of voltages overlap and the second current controlling element is configured to vary the function by which it allows current to flow in dependence on the input voltage; the voltage reference circuit characterised by comprising: a reset input for receiving a reset input; and a third current controlling element connected in series between the first current controlling element and the output, wherein the third current controlling element is configured to allow current to flow in dependence on a voltage received at the reset input. a reset input for receiving a reset input; and a third current controlling element connected in series between the first current controlling element and the output, wherein the third current controlling element is configured to allow current to flow in dependence on a voltage received at the reset input.