A test system can use first and different second driver stages to provide test signals to a device under test (DUT). A compound stage can receive signals from the driver stages and provide a voltage output signal to the DUT, such as via a gain circuit. The compound stage can include a buffer circuit configured to provide a first portion of the voltage output signal based on a first output signal from the first driver stage, and the compound stage can include a transimpedance circuit configured to provide a second portion of the voltage output signal based on a second output signal from the second driver stage. In an example, the gain circuit can receive a superposition signal comprising the first and second portions of the voltage output signal and, in response, provide a test signal to the DUT.

Structures including a photodiode and methods of fabricating such structures. A substrate has a top surface, a well, and a trench extending from the top surface to the well. A photodiode is positioned in the trench. The photodiode includes an electrode that is provided by a first portion of the well. A bipolar junction transistor has an emitter that is positioned over the top surface of the substrate and a subcollector that is positioned below the top surface of the substrate. The subcollector is provided by a second portion of the well.

A multi-stage amplifier including a pre-driver stage, and method of operating the same. In one example, the amplifier includes an output stage with a first output transistor coupled to an oppositely doped second output transistor and to an output terminal. The pre-driver stage includes with a first driver transistor coupled to the first output transistor, and a second driver transistor coupled to the second output transistor. The pre-driver stage also includes a first current mirror and a second current mirror coupled to the first driver transistor and the second driver transistor. The pre-driver stage also includes a first translinear loop having a first translinear loop transistor and a second translinear loop having a second translinear loop transistor coupled to the first output transistor and the second output transistor.

A power amplifier and power amplification circuit are described herein. An illustrative power amplifier is disclosed to include an input terminal, a drive amplifier connected to the input terminal, and an impedance modulator having a capacitance that is adjusted inversely and proportionately relative to a signal output by the drive amplifier, wherein the impedance modulator provides a feedback loop between an output of the drive amplifier and the input terminal.

A power amplifier and power amplification circuit are described herein. An illustrative power amplifier is disclosed to include an input terminal, a drive amplifier connected to the input terminal, and an impedance modulator having a capacitance that is adjusted inversely and proportionately relative to a signal output by the drive amplifier, wherein the impedance modulator provides a feedback loop between an output of the drive amplifier and the input terminal.

A measurement circuit may include a transistor having a first terminal, a second terminal, and a third terminal, wherein the first terminal is coupled to a first reference voltage. The measurement circuit may further include a first operational amplifier including a first input coupled to the second terminal of the transistor and an output coupled to the third terminal of the transistor. The first operational amplifier may further include a second input configured to receive a second reference voltage. The measurement circuit may also include a first unity-gain voltage follower including a second operational amplifier having a first input coupled to the first input of the first operational amplifier. Methods of measuring a threshold voltage, semiconductor devices, and electronic systems are also described.

A measurement circuit may include a transistor having a first terminal, a second terminal, and a third terminal, wherein the first terminal is coupled to a first reference voltage. The measurement circuit may further include a first operational amplifier including a first input coupled to the second terminal of the transistor and an output coupled to the third terminal of the transistor. The first operational amplifier may further include a second input configured to receive a second reference voltage. The measurement circuit may also include a first unity-gain voltage follower including a second operational amplifier having a first input coupled to the first input of the first operational amplifier. Methods of measuring a threshold voltage, semiconductor devices, and electronic systems are also described.

Structures including a photodiode and methods of fabricating such structures. A substrate has a top surface, a well, and a trench extending from the top surface to the well. A photodiode is positioned in the trench. The photodiode includes an electrode that is provided by a first portion of the well. A bipolar junction transistor has an emitter that is positioned over the top surface of the substrate and a subcollector that is positioned below the top surface of the substrate. The subcollector is provided by a second portion of the well.

An apparatus includes a tunable non-Foster matching network having (i) an amplification stage with an amplifier and (ii) a reference reactance coupled in parallel with the amplifier. The non-Foster matching network is configured to provide a negative reactance based on the reference reactance. The amplification stage also includes at least one adjustable circuit element configured to adjust a gain of the amplification stage and thereby adjust the negative reactance. In some cases, the amplification stage may include a common emitter amplification stage having a transistor, and the at least one adjustable circuit element may include an adjustable capacitor and/or multiple adjustable resistors in an emitter circuit of the transistor. In other cases, the amplification stage may include an operational amplifier and multiple resistors configured to set a gain of the operational amplifier, and the at least one adjustable circuit element may include at least one of the resistors.

A (pre) driver circuit includes first and second output terminals configured to be coupled to a power transistor. A differential stage has non-inverting and inverting inputs for receiving an input voltage. The input voltage is replicated as an output voltage across the first and second output terminals as a drive signal for the power transistor. The differential stage includes a differential transconductance amplifier in a voltage follower arrangement configured to provide continuous regulation of a voltage at the first output terminal with respect to the second output terminal.