Analog Devices,inc.

Analog Devices Global

Analog Design Services Limited

Stefan Marinca

Thomas G O'Dwyer

Dennis A Dempsey

Denis Martin O'Connor

Gabriel Banarie

Reference circuits are described. In particular reference circuits that use a plurality of cascaded proportional to absolute temperature, PTAT, cells are described. In the circuits disclosed, currents of the low current density arm of first PTAT cell are mirrored into the high current density arms of a second PTAT cell such that any deviation of current in the low current density arm of the first cell will be replicated as the current in the high current density arm of the second cell. In this way low noise circuits can be provided.

Low noise reference circuit

The present disclosure relates to a PTAT voltage reference circuit and a temperature independent voltage reference circuit in which the effect of transistor base currents on the circuit output is compensated for. This is achieved by a pair of compensation resistors. The base current from one of the pair of transistors is used to increase the voltage drop across one of the compensation resistors. The base current from the other of the pair of transistors is used to decrease the voltage drop across another of the compensation resistors, by an equal amount. The compensation resistors are connected in series with the resistor which reflects the difference in base-emitter voltage (&#x394;V). The circuit output is measured across the series connected resistors. As such, the base currents are compensated for at the output.

Proportional to absolute temperature reference circuit and a voltage reference circuit

Circuits for generating a PTAT voltage as a base-emitter voltage difference between a pair of bipolar transistors. The circuits may form unit cells in a cascading voltage reference circuit that increases the PTAT voltage with each subsequent stage. The bipolar transistors are controlled using a biasing arrangement that includes an MOS transistor connected to a current mirror that provides the base current for the bipolar transistors. A voltage reference is formed by combining a PTAT voltage and a CTAT voltage at the last stage. The voltage reference may be obtained from the voltage at an emitter of one of the bipolar transistors in the last stage.

Method and circuit for low power voltage reference and bias current generator

A bias current generators that may be implemented in low power environments is described. The current generator can be implemented without using resistors and may be used to generate reference currents and voltages. It may also be used to generate voltage references where the output of the circuit is to at least a first order temperature independent.

Low power bias current generator and voltage reference

A proportional to absolute temperature (PTAT) circuit is provided. By judiciously combining circuit elements into two or more cell it is possible to effectively dump bias current into impedance resistive element of a first cell from other cells of the circuit. As a result the circuit as a whole can operate with smaller resistive elements and therefore occupy less area when implemented in silicon. It is also possible to reduce the supply current that is required for providing specific output currents or voltages.

Low power proportional to absolute temperature current and voltage generator

Early effects are intrinsically present in bipolar junction transistors (BJTs). Described are examples of complimentary to absolute temperature (CTAT) and proportional to absolute temperature (PTAT) cells that reduce errors associated with the Early effects that would otherwise be present.

Circuit and method for compensating for early effects

The present disclosure relates to a method and apparatus for generating a voltage reference. More particularly the present disclosure relates to a methodology and circuitry configured to provide an output signal that combines a proportional to absolute temperature component with a complimentary to absolute temperature component to generate a stable output which is not temperature dependent.

Voltage reference circuit

Circuits and method for providing voltage reference circuits that include low drift over time and lower operating voltages are provided. Generally, it is desirable that a reference circuit provide an accurate and precise reference over time. The voltage reference circuits described can provide for good long term stability, operation at lower voltages than prior designs, consistent output voltage with reduced variability due to process changes and mismatches, low noise in the reference voltage, and other advantages.

Low drift voltage reference

A proportional to absolute temperature, PTAT, circuit is provided. By judiciously combining circuit elements it is possible to generate a voltage at an output node of the circuit that is temperature dependent. Such a PTAT circuit can be used as a temperature sensor or can be combined with other temperature dependent circuits to provide a voltage reference.

Proportional to absolute temperature circuit

A system provides for a voltage reference having a small temperature coefficient spread. The voltage reference includes a PTAT voltage trimming circuit that accurately trims the CTAT voltage component of the bandgap type voltage reference. The voltage trimming circuit includes two bipolar transistors that are biased by biasing currents to create a specific base-emitter voltage difference at an output. The bias currents can be digitally trimmed by a current digital-to-analog ('DAC') converter. This may result in the ability to trim the voltage reference at a single temperature, without the need to trim at two or more temperatures.

Precision CMOS voltage reference

A system and method are provided for a more accurate bandgap voltage reference wherein the first and second order errors are corrected simultaneously. By using the components included in the correction of the first order error, the second order errors are corrected, advantageously providing less process variability.

Second order correction circuit and method for bandgap voltage reference

A system and method are provided for a PTAT cell with no resistors which can operate at low power, has less sensitivity to process variation, occupies less silicon area, and has low noise. Further, a system and method are provided to scale up the reference voltage and current through a cascade of unit cells. Still further, a system and method are provided for PTAT component to be fine-tuned, advantageously providing less process variability and less temperature sensitivity.

A reference circuit configured to provide a reference value. The circuit includes a first circuit unit which is configured to provide a first electrical representation that varies linearly with temperature and has a crossover point where its polarity relative to zero changes from a negative value to a positive value. A second circuit unit is configured to provide a second electrical representation that varies linearly with temperature. The first and second circuit units are operable for facilitating combining the first and second electrical representations such that the combination has a value corresponding to the value of the second electrical representation at a reference temperature.

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Limerick, Ireland

Stefan Marinca