A pull-down circuit uses an npn transistor operating at close to saturation and the collector/emitter voltage is used as the pull-down voltage. To keep this within strict limits the npn transistor is connected in circuit with other transistors and resistors as well as a current source that generates a current proportional to absolute temperature. By selecting the values of the resistors and transistor parameters the collector/emitter voltage may be kept stable within a small range over wide temperature variation.