Integrated amplifier with adjustable offset voltage

A field effect transistor with adjustable voltage characteristics comprising:

• a substrate of a first conductivity type;
• a channel region of a second conductivity type in said channel region
• a first and second separated drain regions of said second conductivity in said channel region opposite said source region;
• a gate region of said first conductivity type in said channel region between said source region and said first and second drain regions;
• a drain conductor;
• a fusible means connecting said second drain region to said drain conductor;
• and
• an impedance means connecting said first drain region to said drain conductor for steering current to said fusible means when a sufficient voltage is applied to across said gate region and said drain conductor to forward bias said gate and drain regions to conduct a current sufficient to blow said fusible means.

A method of adjusting the voltage characteristics of a field effect transistor comprising:

• forming the drain of said field effect transistor with at least a first and second separated drain segments;
• connecting said second drain segment to a drain connector by a fusible element;
• connecting said first drain segment to said drain conductor by an impedance capable of steering current to said fusible element during the next step;
• and
• applying a voltage across said gate and said drain conductor sufficient to create a current sufficient to blow said fusible element thereby disconnecting said second drain segment from said drain conductor and altering the voltage characteristics of said field effect transistor.

A method of adjusting the voltage characteristics of a field effect transistor comprising;

• forming the drain of said field effect transistor with at least a first and second separated segments;
• connecting said second drain segment to a drain conductor by a fusible element;
• and
• applying a voltage across said gate, second drain segment and said fusible element sufficient to create a current sufficient to blow said fusible element thereby disconnecting said second drain segment from said drain conductor and altering the voltage characteristics of said field effect transistor.

In an amplifier including first and second separate current paths having a predetermined differential voltage offset therebetween in the absence of any input signals to said operational amplifier, the improvement in each current path comprising:

• a first transistor having a base, collector and emitter;
• a second transistor having a base, collector and emitter;
• said bases being connected together;
• said emitter-collector path of said first and second transistors being connected in parallel to each other in said current paths;
• fusible means interconnecting said second transistor's emittercollector path and said current path;
• and
• impedance means interconnecting said first transistor's emittercollector path and said current path for steering the current to said fusible means produced when a voltage is applied across the base, said fusible means and said impedance means to blow said fusible means and alter said voltage offset.

A method of adjusting the voltage offset between two current paths of an amplifier comprising:

• connecting the emitter-collector paths of two transistors in parallel in each of said current paths;
• connecting a fusible element to the collector of one of said transistors in each of said paths;
• connecting to the collector of the other transistor in each of said paths an impedance capable of steering current to said fusible element during the next step;
• and
• applying a voltage across the bases, collectors, fusible element and impedance of one of said current paths to forward bias said base to collector junctions and create a current sufficient to blow said fusible element thereby disconnecting said one transistor from said current path and altering the offset voltage.

In an amplifier including first and second separate current paths having a predetermined differential voltage offset therebetween in the absence of any input signals to said amplifier and in each of said current paths, an input transistor means having a conduction path and a control electrode, the improvement being said input transistor means each comprising:

• two transistors having their conduction paths connected in parallel in a respective current path and their control electrode tied together as an input;
• a fusible conductive means interconnecting one end of the conduction path of one of the transistors to said current path;
• and
• impedance means interconnecting a corresponding end of the conduction path of the other transistor to said current path for steering the current to said fusible conductive means produced when a voltage is applied across said control electrodes and said one end of the conduction path to forward bias a p-n junction of said transistors which is reversed biased in the normal operation of the transistor to blow said fusible conductive means and alter said voltage offset.