Abstract: An adaptive reference threshold detector for sensing a drop of predetermined magnitude in the level of an input signal from its peak value during an interval of time. A capacitor, diode coupled to the output of a voltage follower, is charged to a level coincident with the maximum input signal voltage during the time interval of interest. The voltage stored thereon is coupled through a negative feedback arrangement and resistive divider network to one port of a voltage comparator. The input signal itself serves as the second input to this voltage comparator circuit. A logic level signal is generated by this comparator when the difference between its two input port signals exceeds a predetermined value.

Abstract: A silicon junction diode is used as one element of a resistance bridge to rm the temperature sensing element of an electronic thermostat. Current through the diode is maintained at approximately constant value so that the negative temperature coefficient characteristic of the diode can be utilized. The values of the fixed resistors in the bridge are selected so as to provide a null at a preselected temperature. Used in conjunction with a voltage comparator circuit having positive feedback, a digital control signal is provided whenever the temperature of the sensing element rises above the preselected null value. The addition of a single NOR gate allows the combination of this digital control signal with an external control signal.