Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Patent
1997-11-10
1999-10-05
Kim, Jung Ho
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
327513, 327539, 323312, 323315, G05F 110
Patent
active
059630825
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a circuit arrangement for producing a D.C. current.
For electronic circuit arrangements to be inserted into battery-operated devices, a lowest possible energy consumption is to be aimed at for economic and ecological reasons. Therefore, electronic circuits which are designed for operation with low supply voltages and low power consumption when in operation have become very important for such devices. In this respect, the energy supply provided by only a single battery cell is aimed at while a D.C. voltage converter for increasing the supply voltage is dispensed with. Under these conditions, an electronic circuit whose voltage is supplied in this manner is to remain operable without any limitations even with a supply voltage down to about 0.9 volt, while the nominal value of the supply voltage is set to 1 volt, for example. When taking the fact into account that for bipolar transistors the base-emitter voltages in the conductive state are typically about 0.7 volt, there is the necessity for the use mentioned above to create specific circuit configurations because, for example, many transistor circuits are capable of operating only with considerably higher supply voltages.
In many applications it is necessary to have stabilized D.C. currents as current references, while these stabilized D.C. currents are to be independent of variations of the supply voltage, so that, for example, variations of the voltage produced by the battery, caused by different charging conditions of the battery must not have any influence on the function of the powered electronic circuits.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the invention to provide a circuit arrangement which can be used as a current reference, which circuit arrangement can be used for very low supply voltages, preferably around 0.9 volt, has a simple structure, shows a stable operating behavior and offers a reference current with a negative temperature coefficient.
According to the invention, this object is achieved by a circuit arrangement for producing a D.C. current, comprising current led via an input resistor, and which comprises a current source transistor whose base-emitter path is arranged in parallel with the input resistor and whose collector electrode forms an output of the current-source stage, on which output an output current is offered, current-source stage to a working impedance, on which working impedance a control voltage is produced in response to this output current, voltage, and having at least two outputs simultaneously controlled by the control voltage, on which outputs mutually proportional currents are offered of which a first current forms the measuring current.
At this point there is observed that from the article "A Curvature-Corrected Low-Voltage Bandgap Reference" published in IEEE Journal of Solid State Circuits", vol. 28, no. 6, June 1993, pages 667 to 670, more particularly, page 668, FIG. 3, a circuit arrangement for producing a D.C. current is known which is also provided as a supply voltage down to one volt. This circuit arrangement comprises an npn transistor whose base-emitter path is connected in parallel with a resistor which resistor is passed through by a part of a current flowing to a branch of a current bank. This branch of the current bank comprises a pnp transistor which is connected in the form of a current mirror circuit to a further pnp transistor arranged as a diode. This pnp transistor arranged as a diode is fed by a further npn transistor whose base electrode is connected to the collector electrode of the former npn transistor. This connection is fed by a current source.
It has appeared that the known circuit arrangement shows a great tendency to oscillate despite thorough compensation measures and is thus unsuitable for use as a current reference.
In the circuit arrangement according to the invention, a closed-loop control circuit is formed via the current source, the current bank and the current mirror stage, which control circuit provide
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Gunawan et al., "A Culvature-Corrected Low-Voltage Bandgap Reference" IEEE Journal of Solid-State Circuits, vol, 28, No. 6, Jun. 1993.
Dick Burkhard
Wichern Andreas
Kim Jung Ho
Slobod Jack D.
U.S. Philips Corporation
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