Abstract: A method for calibrating a digital temperature sensor circuit, the circuit comprising an analogue temperature sensing means, an internal reference voltage source and an analogue-to-digital converter (ADC). The ADC is arranged to receive respective signals from the analogue temperature sensing means and the reference voltage source and output a digital signal indicative of the ambient temperature. The method comprises the steps of determining the value of the internal reference voltage outputted by the reference voltage source, comparing it with the desired reference voltage value, and adjusting the reference voltage source in response to the result of the comparison step. Such an electrical voltage mode calibration can significantly reduce production costs, as it can be performed much faster than a traditional thermal calibration. The method can be applied to a sensor that produces a PTAT voltage that has to be compared to a temperature-independent bandgap reference voltage.

Abstract: A bias circuit for use in bandgap voltage reference circuits and temperature sensors comprises a pair of transistors (Q, Q2), the first of which (Q1) is arranged to be biased at an emitter current lbias, and the second of which (Q2) is arranged to be biased at an emitter current of m.lbias. The circuit is arranged such that the difference between the base-emitter voltages of the transistors is generated in part across a first resistance means having a value Rbias and in use carrying a bias current equal to lbias and in part across a second resistance means of value substantially equal to Rbias/m and in use carrying a current equal to the base current of the second transistor. This results in use in a bias current Ibias which, when used to bias a substrate bipolar transistor via its emitter, produces a collector current therefrom which is substantially PTAT and a base-emitter voltage which is substantially independent of the forward current gain of the substrate bipolar transistor.

Abstract: A bias circuit for use in bandgap voltage reference circuits and temperature sensors comprises a pair of transistors (Q, Q2), the first of which (Q1) is arranged to be biased at an emitter current lbias, and the second of which (Q2) is arranged to be biased at an emitter current of m.lbias. The circuit is arranged such that the difference between the base-emitter voltages of the transistors is generated in part across a first resistance means having a value Rbias and in use carrying a bias current equal to lbias and in part across a second resistance means of value substantially equal to Rbias/m and in use carrying a current equal to the base current of the second transistor. This results in use in a bias current Ibias which, when used to bias a substrate bipolar transistor via its emitter, produces a collector current therefrom which is substantially PTAT and a base-emitter voltage which is substantially independent of the forward current gain of the substrate bipolar transistor.

Abstract: A method for calibrating a digital temperature sensor circuit, the circuit comprising an analogue temperature sensing means, an internal reference voltage source and an analogue-to-digital converter (ADC). The ADC is arranged to receive respective signals from the analogue temperature sensing means and the reference voltage source and output a digital signal indicative of the ambient temperature. The method comprises the steps of determining the value of the internal reference voltage outputted by the reference voltage source, comparing it with the desired reference voltage value, and adjusting the reference voltage source in response to the result of the comparison step. Such an electrical voltage mode calibration can significantly reduce production costs, as it can be performed much faster than a traditional thermal calibration. The method can be applied to a sensor that produces a PTAT voltage that has to be compared to a temperature-independent bandgap reference voltage.

Abstract: When a reference signal is generated for a digital-to-analog converter in the feedback path of a sigma-delta modulator, the reference signal can contain modulated error signals, for example when the reference generator implements dynamic element matching. By controlling the reference signal generation in dependence on the bitstream output from the sigma-delta modulator, the effects of intermodulation of the reference signal with the bitstream can be reduced.

Abstract: Chopper chopper-stabilized instrumentation and operational amplifiers having ultra low offset. The instrumentation amplifiers use current-feedback, and include, in addition to a main chopper amplifier chain, a chopper stabilized loop for correcting for the offset of the input amplifiers for the input signal and for receiving the feedback of the output voltage sense signal. Additional loops, which may include offset compensation and autozeroing loops, may be added to compensate for offsets in the chopper stabilized loop for correcting for the offset of the input amplifiers. Similar compensation is disclosed for decreasing the offset in operational amplifiers.

Abstract: Frequency stabilization of chopper-stabilized amplifiers using multipath hybrid double-nested Miller compensation. The compensation may provide a desired 6 dB/oct roll off for both instrumentation amplifiers and operational amplifiers. Various embodiments are disclosed.

Abstract: A transconductance (g.sub.m) control circuit for bipolar or CMOS rail-to-rail input stages is provided. The g.sub.m is controlled by the use of multiple input pairs and can be used in CMOS or bipolar technology. In CMOS the g.sub.m -control works regardless of the operating region of the MOS transistor, whether it is weak, moderate or strong inversion.