US 4,072,870 A · Comparison circuit having programmable hysteresis

Abstract

A differential amplifier circuit suitable to be fabricated in monolithic integrated circuit form and having externally programmable, symmetrical input hysteresis. The differential amplifier circuit includes a differential input stage having a resistor coupled between the emitters of the differential transistors. A steering circuit comprising a second differential stage is connected across the resistor at the outputs of the collectors thereof. A differential to single ended converter circuit is utilized to provide output drive to an output multiple collector transistor from the differential input stage. A switching circuit is coupled between one collector of the output transistor to the steering circuit for selectively switching this circuit for steering current through the resistor. An external voltage is coupled across a component of the steering circuit for deriving temperature independent hysteresis. By switching the steering circuit, symmetrical hysteresis is obtained about a given level.

Claims15

Dependent claims

A comparison circuit having symmetrical hysteresis, comprising:

a differential input stage including a pair of differentially coupled devices each having first, second and input terminals, and circuit means coupled between said first terminals of said devices for establishing a hysteresis voltage thereacross in response to a current of predetermined magnitude being selectively steered therethrough, said devices receiving first and second applied input signals at said respective input terminals;
output circuit means coupled to said second terminals of said devices being responsive to said input signals for providing a two discrete level output signal at first and second outputs respectively;
and
current steering means coupled from said first output of said output circuit means across said circuit means for selectively steering said current through said circuit means in first and second directions depending upon the operating state of said output signal from said output circuit means.

1 more element

A comparison circuit suitable to be fabricated in monolithic integrated circuit form having symmetrical input hysteresis controlled by an externally applied control voltage comprising:

comparator means responsive to applied input signals for producing output signals of two discrete states, each state being indicative of predetermined threshold conditions of said input signals including resistive means across which an input offset voltage is developed to provide the symmetrical input hysteresis, the magnitude and polarity of said input offset voltage being a function of the magnitude and direction of current flow through said resistive means;
steering circuit means coupled across said resistive means having input terminals to receive, respectively, switching signals for selectively steering said current through said resistive means to change the polarity of said input offset voltage;
and
switching circuit means coupled between said comparator means and said input terminals of said steering circuit means for providing said switching signals in response to said states of said output signals from said comparator means, said switching means having an input to receive a control voltage, the control voltage being coupled through said switching circuit means to said steering circuit means such that a current is developed the magnitude of which is indicative of said control voltage.

1 more element

Dependencies are inferred from the claim text.

Comparison circuit having programmable hysteresis

Life of this patent

Comparison circuit having programmable hysteresis

Life of this patent

Abstract

Claims15