Patent ID: 7145318

Claim:
A control circuit for a negative voltage regulator including: a stable positive voltage reference potential; a first voltage divider including a first resistor having a first resistance and coupled to the positive voltage reference potential in series with a second resistor having a second resistance and coupled to ground; a second voltage divider including a third resistor having the first resistance and coupled to the positive voltage reference potential in series with a fourth resistor having the second resistance, the fourth resistor in series with a fifth resistor having a third resistance and coupled to a negative voltage potential; and a comparator having an inverting input coupled to the first voltage divider between the first and second resistors and a non-inverting input coupled to the second voltage divider between the third and fourth resistors; wherein the values of the first and third resistors are equal, the values of the second and fourth resistors are equal, and the value of the fifth resistor is chosen such that it will drop a voltage equal in magnitude to a target voltage to be regulated when the voltage regulator output is equal to that target voltage.