Texas Instruments Corporation

Wally Meinel

Vadim Valerievich Ivanov

Junlin Zhou

David Baum

Vidim V Ivanov

A multi-stage differential amplifier with rail-to-rail input may utilize an output stage including first and second low-voltage rated transistors and first and second high-voltage transistors. The first low-voltage rated transistor and the first high-voltage rated transistor may be connected in series, and the second low-voltage rated transistor and the second high-voltage rated transistor may be connected in parallel. The low-voltage rated transistors are biased by signals provided by the input stage. In this way, the input stage controls the biasing of the low-voltage rated transistors in the output stage, thereby increasing the overall gain and speed of the amplifier system.

Operational amplifier output stage and method

A precision operational amplifier operating in single supply mode, including a single differential transistor input pair and a cascoded CMOS transistor pair, stabilizes the drain-to-source voltage of the input transistor pair to ensure a stable off-set voltage and increased power supply and common mode rejection. The precision amplifier biases the cascoded CMOS transistor pair in accordance with the stabilized drain-to-source voltage of the differential transistor input pair. Such biasing may take the form of body biasing or biasing the gates of the cascode CMOS transistor pair to ensure that the CMOS transistor pair remain in the active region of operation when the common mode supply voltage approaches zero.

Operational amplifier input stage and method

An exemplary trimming circuit can be further simplified to include a single current source to provide for trimming of offset and temperature drift in a device, such as an op amp, voltage reference and the like. A single temperature-dependent current source is trimmed to a predetermined value, for example to zero, at a first temperature, and then the current from the temperature-dependent current source is used to trim output parameters, i.e., adjust the output variables, to a desired value at a second temperature. An exemplary trimming circuit comprises a temperature-dependent current source I , a current switch and a device to be, trimmed. The current switch is configured to suitably facilitate the trimming of the trimmed device through coupling of a fraction or multiple of the current signal from temperature-dependent current source I to one or more offset-control terminals of the trimmed device.

Method and circuit for trimming offset and temperature drift

A trimming circuit and method of trimming is provided for offset and temperature drift trimming of an op amp or voltage reference device, having an input stage, on at least two different temperatures. The trimming circuit has a current source stage, having first and second current sources which are trimmed at a first temperature, in a first step, to balance the currents of the first and second current sources. The two current sources are configured to be selectively connected, in a second step and at the first temperature, to the offset-control terminal(s) of the input stage and thereby to trim the output of the input stage. The first and second current sources also have different temperature coefficients and are interchangeable with other current sources to facilitate changing, in a third step, the temperature coefficient of one of the two current sources to facilitate offset trimming at a second temperature.

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Wally Meinel