Differential amplifier
AssigneeRaytheon Company
InventorsCharles L. Vinn, Thinh C. Nguyen
Life of this patent
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Abstract
An improved differential amplifier having circuitry to enhance the slew rate and to provide a means for nulling the offset voltage during fabrication of the amplifier as an integrated circuit. The differential amplifier comprises an input stage connected to a current mirror. A slew rate enhancement circuit injects current into selected points of the circuit when the input voltage exceeds a predetermined threshold. An offset trim circuit injects a selected amount of current into the current mirror to alter the current flow between the input stage and the current mirror, thereby reducing the offset voltage. The selected amount of current is dictated by diodes which may be permanently shorted at various stages during fabrication, both before and after the amplifier is enclosed in an IC package.
Claims4
In a differential amplifier of the type having:
- (a) an input stage;
- (b) a current mirror coupled to the input stage via first and second leads wherein a positive input voltage increases the current in the first lead and a negative input voltage decreases the current in the first lead;
- and
- (c) a gain stage connected via a third lead to the second lead wherein an increase in current in the first lead increases the flow of current in the third lead in the direction out of the gain stage and a decrease in current in the first lead increases the flow of current in the third lead in a direction into the gain stage, an improved offset trim circuit comprising:
- (i) means for producing an adjustment current, said means comprising:
- (a) a plurality of sources of current;
- (b) a like plurality of diodes, each diode connecting one of the plurality of sources of current to a common node;
- (c) a first output diode connecting the common node to a first output line;
- and
- (d) a second output diode connecting the common node to a second output line;
- (ii) wherein the first output line is connected to the first lead of the current mirror;
- and
- (iii) wherein the second output line is connected to the second lead of the current mirror.
Dependencies are inferred from the claim text.