Protection voltage generating circuit with monotonic and stable power supply voltage behavior

A method of protecting devices at a node of a protected circuit from an over-voltage or under-voltage condition, the method comprising:

• generating, by a first circuit, a first voltage from a power supply voltage
• generating, by a second circuit, a second voltage from the power supply voltage, wherein the first voltage and the second voltage have a differing dependence on the power supply voltage so that a difference between the first voltage and the second voltage changes sign for a particular value of the power supply voltage;
• generating a first output voltage by a first amplifier circuit that receives the first voltage;
• generating a second output voltage by a second amplifier circuit that receives the second voltage, wherein the second amplifier circuit generates a second output voltage;
• providing negative feedback to the second amplifier circuit from the second amplifier circuit to the first amplifier circuit;
• providing negative feedback to the first amplifier circuit to the second amplifier circuit;
• and
• generating a protection voltage by an output circuit that receives the first output voltage from the first amplifier circuit and the second output voltage from the second amplifier circuit and generates the protection voltage according to a maximum or a minimum value among the first output voltage and the second output voltage, so that the protection voltage is monotonic with respect to variation of the power supply voltage in a region of the power supply voltage including the particular value of the power supply voltage.