HIGH VOLTAGE FUNCTIONAL COMPARATOR

• US 3,628,059 A
• Filed: 06/01/1970
• Issued: 12/14/1971
• Est. Priority Date: 06/01/1970
• Status: Expired due to Term

• Current Assignee: George G.Y. Niu
• Original Assignee: George G.Y. Niu
• Inventors: Niu, George G. Y.
• Primary Examiner(s): Zazworsky, John
• Application Number:
  US05/041,963
• Time in Patent Office: 561 Days
• Field of Search: 307/235 328/146,147 330/3D
• US Class Current: 327/72
• CPC Class Codes: H03K 3/2897 with an input circuit of differential configuration

Abstract

A comparator circuit has an hysteresis relationship between its two-level output signal and the input signal. As a result, the level of the output signal is substantially independent of noise on the input signal. By changing the value of a resistor the amount of hysteresis in the circuit is changed.

Claims

1. Structure which comprises a two-state current source capable of either drawing the current I2 or drawing any current, said two-state current source possessing an input lead;

a first current source which supplies a current I1, said first current source possessing an output lead which is connected to the input lead of said two-state current source;

a source of reference potential connected through a hysteresis resistor to the output lead of said first current source and the input lead of said two-state current source; and

means for switching said two-state current source either on or off, in response to an input signal going selected amounts above or below, respectively, said reference potential, said two-state current source not drawing any current when said input signal goes to one side of said reference potential by a first selected amount, thereby forcing the current I1 through said source of reference potential, said two-state current source drawing the current I2 when said input signal goes to the other side of said reference potential by a second selected amount thereby allowing said two-state current source to draw the current from said first current source plus an additional current from said source of reference potential.

2. Structure as in claim 1 wherein said one side is beneath said reference potential and said other side is above said reference potential.

3. Structure as in claim 1 wherein said two-state current source when on draws the current I2, where I2 equals 2I1.

4. Structure as in claim 1 wherein said source of reference potential supplies the current I1 to said two-state current source when said two-state current source draws the current I2.

5. Structure as in claim 2 wherein said first and second selected amounts equal one-half I1 times the hysteresis resistor connecting said reference potential to the output of said first current source and the input of said two-state current source.

6. Structure as in claim 5 wherein said means for switching said two-state current source comprises an input circuit, said input circuit comprising:

a second current source supplying a given current; and

a first and a second pair of matched transistors, each pair comprising a first and a second transistor, the emitters of the transistors in said first pair being coupled to said second current source, the base of the first transistor in said first pair being connected to the source of said input signal and the base of said second transistor in said first pair being connected to said source of reference potential, the emitters of said transistors in said second pair being coupled to said second curreNt source, the bases of said first and second transistors in said second pair being connected to the emitters of said first and second transistors respectively in said first pair, and the collectors of the first transistors in said first and second pairs being connected through a first resistor to a source of potential, the collectors of the second transistors in said first and second pairs being connected through a second resistor to said source of potential.

7. Structure as in claim 6 wherein:

the emitters of the first and second transistors in said first pair are coupled by first and second resistors to said second current source;

the base of the first transistor in said first pair is connected by a third resistor to said source of said input signal;

the base of the second transistor in said first pair is connected by the hysteresis resistor to said source of reference potential; and

the collectors of the first transistors in said first and second pairs are connected to the collectors of the second transistors in said first and second pairs by two diodes, oppositely poled in parallel.

8. Structure which comprises:

means for generating a reference potential Eref;

means for producing a first constant current I0;

means, responsive to an input signal Ein, for shunting said first constant current, I0, through a first path or a second path;

means for producing a second constant current I1; and

two-state means, responsive to the path traveled by said first constant current I0, for drawing either a current 2I1 or no current, said means for generating a reference potential drawing through a hysteresis resistor the current I1 from said means for producing a second constant current I1 and said two-state means drawing no current when said input signal Ein goes to less than Eref by a first given amount, and said two-state means drawing the current 2I1 when said input signal Ein goes above Eref by a second selected amount, said second constant current source supplying the current I1 to said two-state means and said reference source supplying through said hysteresis resistor the remaining current I1.