Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Patent
1997-02-26
1999-08-31
Cunningham, Terry D.
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
327539, 327545, 327540, G05F 110
Patent
active
059458712
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a process for temperature stabilization of a reference voltage and, in particular, to a process in which, in a first time interval, a current with a first amperage and, in a second time interval, a current with a second amperage are alternately provided to a diode or pn junction, preferably the base-emitter diode of a bipolar transistor. During the first and second time intervals, the voltages at the diode or the pn junction are supplied to the input of an analysis circuit. In the analysis circuit, the difference between the two voltages obtained through the first and the second amperages is formed and added in a weighted manner to the voltage obtained through one of the two amperages. The result is then provided as the output of the analysis circuit.
2. Description of the Related Art
Bandgap reference processes based on the principle of temperature compensation through weighted addition of two voltages U1 and U2 with opposing temperature coefficients are well known. The weighting factors K1 and K2 are chosen in such a way that the effects on these voltages due to the temperature T mutually cancel each another. The reference voltage Uref is thus represented as follows:
U.S. Pat. No. 5,059,820 discloses a circuit configuration in accordance with such a known bandgap reference process in which, for temperature stabilization of a reference voltage, two different amperages are alternately provided, by means of two synchronized current sources, to a single pn junction formed by the base-emitter diode of a bipolar transistor. The voltage drop at the pn junction is supplied to an analysis circuit. In this way, owing to the use of only one diode, it is not necessary to take into account variation or scatter of the characteristic data of a second diode. It is thereby possible to greatly reduce the scatter of the absolute value of the reference voltage as well as its temperature dependence. A particular advantage of this process is that it is only weakly dependent on resistance relations and current density relations.
PCT Patent Application WO 82/02806 discloses that, for the voltages U1 and U2 with opposed temperature effect, it is known to use the voltage drop U.sub.be at the base-emitter diode of a bipolar transistor, given the current density and the voltage difference DU.sub.be between these and the base-emitter diode of another bipolar transistor, to which a different amperage is applied. The weighted addition of the voltages U1 and U2 occurs in an analysis circuit by means of an operational amplifier connected to resistors.
The drawbacks of this process lie, first, in the use of at least two base-emitter diodes, since very different results can thereby be obtained due to scatter of the characteristic data, and, second, in the poor implementation of the process in the case of integrated circuits in CMOS technology, since the resistors of the analysis circuit in this technology cannot be fabricated with adequate precision.
SUMMARY OF THE INVENTION
The above-discussed problems are overcome in accordance with the present invention by applying a first constant amperage to a diode or ph junction during both first and second prespecified time intervals and by applying a second constant amperage during the second prespecified time interval in addition to the first amperage.
In further accordance with the invention, in the analysis circuit, the voltage that is applied to the diode during one of the time intervals is read and, during subsequent time interval is stored. In this way, it is possible to accomplish in a simple way the weighted addition of the voltage or voltage difference that is successively present.
The invention also provides a circuit configuration for carrying out the process. A drawback of known circuit configurations is the deterioration of the temperature stability through the offset voltage, which is mostly temperature dependent as well, in the operational amplifier used in the analysis circuit. A circuit
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Kausel Wilfried
Kremser Johann
Peev Rumen
Cunningham Terry D.
National Semiconductor Corporation
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