One aspect of the present technology relates to a device. The device includes a sensor having an anode and a cathode. An operational amplifier (op-amp) having a single-ended output terminal, a non-inverting input, and an inverting input, is operatively coupled to one of the anode or the cathode of the sensor by the inverting input. A feedback resistor having a resistance of at least approximately one giga-ohm (1 GΩ) is operatively coupled between the single-ended output terminal and the inverting input of the op-amp. A grounded field shunt is positioned adjacent to the feedback resistor. The op-amp, grounded field shunt, and feedback resistor are disposed within an electrical shield enclosure. The single-ended output terminal of the op-amp terminates outside of the electrical shield enclosure.

A method of operating an amplifier circuit having a transformer arranged so as to establish a magnetically coupled feedback loop between and output of an amplifier and an input of the amplifier. The method includes providing a DC bias current to the amplifier, and further includes increasing the DC bias current to improve a linearity of the amplifier circuit wherein a transfer gain of the amplifier circuit remains constant when the DC bias current is increased. A loop gain of the magnetically coupled feedback loop is set by selecting a coupling factor and turn-ratio of the transformer.

An amplifier circuit includes an amplifier having an amplifier input and an amplifier output. The amplifier circuit includes a transformer having a primary winding in series with the amplifier output and a secondary winding coupled to the amplifier input. The primary winding and the secondary winding are arranged such that a portion of a magnetic field generated by the primary winding couples to the secondary winding through a magnetically coupled feedback loop, thereby providing feedback from the amplifier output to the amplifier input. An output load arrangement is connected to the primary winding wherein the output arrangement includes a balun. The amplifier circuit may be implemented as an integrated circuit and where the primary and secondary windings are integrated in different metal layers of the integrated circuit or are otherwise arranged to effect a desired degree of magnetic coupling and feedback from the amplifier output to the amplifier input.

An amplifier circuit includes an amplifier having an amplifier input and an amplifier output. A transformer disposed to provide a signal for driving a load includes a primary winding in series with the amplifier output. A secondary winding of the transformer is coupled to the amplifier input where the primary winding and the secondary winding are arranged such that a portion of a magnetic field generated by the primary winding couples to the secondary winding so as to establish a magnetically coupled feedback loop from the amplifier output to the amplifier input. A loop gain of the magnetically coupled feedback loop is substantially independent of an impedance of the load and is defined at least in part by a coupling factor and turn-ratio of the transformer. The load may be included within an output load arrangement including a balun.

A stacked amplifier circuit includes an input stage having first and second input ports respectively defined by inputs of first and second transistors. A transformer arrangement includes first and second primary windings and first and second secondary windings. The first secondary winding is connected to an output of the first input transistor and the second secondary winding is connected to an output of the second input transistor. Portions of the magnetic fields generated by the primary windings couple to their respective secondary windings. An output stage is AC coupled to the first and second secondary windings and has an output connected to the first and second primary windings. The input stage and the output stage are arranged in a stacked configuration such that a bias current of the output stage is reused as bias current for the input stage.

An amplifier circuit including a first amplifier having a first amplifier input and a first amplifier output and a transformer including a first transformer component having a first primary winding in series with the first amplifier output and a first secondary winding coupled to the first amplifier input. The first primary winding and the first secondary winding are arranged such that a portion of a first magnetic field generated by the first primary winding couples to the first secondary winding through a first magnetically coupled feedback loop. The transformer further includes a second transformer component having a second primary winding in series with an output of a second amplifier and a second secondary winding coupled to an input of the second amplifier input. A portion of a second magnetic field generated by the second primary winding couples to the second secondary winding through a second magnetically coupled feedback loop.

An apparatus include one or more DACs and a resistor divider are configured to generate a variable bias voltage V.sub.BIAS with respect to a CM voltage V.sub.CM. The CM voltage V.sub.CM is applied to a cathode of one or more thermopiles or a negative input of one or more amplifiers to prevent saturation and over range of one or more low voltage readout amplifiers and one or more ADCs.

A device includes an amplifier having inverting and non-inverting inputs and an output. The device includes a capacitor coupled to a first node and to ground, a resistor coupled to the first node and the amplifier output, and a first switch coupled to the first node and a current sink, which is coupled to ground. The device includes AND gate having inputs and an output coupled to control terminal of first switch. The device includes a first comparator having non-inverting and inverting inputs and an output coupled to an AND gate input; a second comparator having a non-inverting input coupled to the amplifier output, an inverting input coupled to a transistor stack, and an output coupled to an AND gate input; and a second switch coupled to the transistor stack and to a current source, the second switch having a control terminal coupled to the first comparator output.

A feedback ammeter, which may be included in a source measure unit or a digital multi-meter, for example, including an operational amplifier having an input and an output and a feedback path electrically coupled between the output and the input of the operational amplifier. The feedback path includes a first non-linear device to allow the measurement of decades of current. The ammeter also includes an amplifier electrically coupled to the input of the operational amplifier and the output of the operational amplifier, a second non-linear device electrically coupled to an output of the amplifier, and a resistor electrically coupled between the second capacitor and the input of the operational amplifier. A constant resistance input impedance is established using the second non-linear device that can adjust the circuit gain.

Various embodiments of the present technology comprise a method and apparatus for a dual mode operational amplifier. According to various embodiments, the operational amplifier functions as both a fully-differential amplifier and a single-ended amplifier. The operational amplifier may comprise additional transistors that function as switches, which can be selectively operated according to a desired mode.