Circuit arrangement for amplifying a differential voltage...

Details Circuit arrangement for amplifying a differential voltage... Circuit arrangement for amplifying a differential voltage...

1999-02-17

2001-01-23

Shingleton, Michael B (Department: 2817)

Amplifiers

With semiconductor amplifying device

Including differential amplifier

C330S289000, C330S146000

Reexamination Certificate

active

06177840

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a circuit arrangement for amplifying a differential voltage signal in an output signal proportional to a voltage difference.
BACKGROUND INFORMATION
Circuit arrangements for amplifying a differential voltage signal in an output signal proportional to a voltage difference are known. In these conventional circuits, the voltages to be compared are applied to two inputs of the circuit arrangement, and a current signal proportional to a resulting voltage difference is generated at an output of the circuit arrangement. Cross-coupled circuits of transistors are usually used, the inputs of the circuit arrangements being respectively connected to the base of one of the transistors. If a voltage difference exists at the two inputs, a cross current proportional to the voltage difference is generated. That current can be picked off at an output of the circuit arrangement, and can be converted into a voltage by connecting the output to a resistive load. Circuit arrangements of this kind are suitable, for example, for the analysis of sensor signals with which at least one physical and/or chemical measured value can be analyzed. Because of the cross-coupled connection of the transistors, it is possible to achieve amplification of the differential signal with high linearity in terms of temperature when using transistors which exhibit high current gain. When such circuit arrangements are used in integrated circuits, however, the transistors of the cross-coupled circuit generally possess a relatively low current gain, which results in a nonlinearity in the differential voltage-dependent gain of the circuit arrangement. One reason lies in a temperature dependence of the base currents of transistors in integrated circuits.
SUMMARY
The circuit arrangement according to the present invention has the advantage that even when transistors in integrated circuits are used, a precise differential voltage analysis can be accomplished with a relatively low current gain. It is particularly advantageous that circuit arrangements can be achieved in very confined spaces with a substantially temperature-independent characteristic curve by way of components, in particular transistors, that can be manufactured in large quantities and relatively economically using bipolar processes. The fact that a compensation circuit whose temperature behavior corresponds to the temperature behavior of cross resistances of the circuit arrangement is associated with each of the inputs of the circuit arrangement makes it advantageously possible to compensate for the nonlinearities which usually occur in the integrated-technology circuit arrangement.
In an example embodiment of the present invention, provision is made for each compensation circuit to comprise a compensation resistor, the compensation resistor having approximately three times the value of a cross resistor of the circuit arrangement. This compensates in particularly simple fashion, i.e., by way of one additional compensation resistor in each case, for a nonlinear temperature behavior of the circuit arrangement. The compensation resistors can easily be integrated into the patterning process of integrated circuits. The compensation circuit also may include a transistor whose base is connected to the signal source furnishing the voltages to be compared, and whose emitter is connected to the compensation resistor. The advantageous result is that because of the emitter connection of the transistor of the compensation circuit, an internal resistance of the signal source is negligible, and thus exerts no influence on the gain characteristics of the circuit arrangement.
Provision is also made, in an example embodiment of the present invention, for the compensation resistors to be circuit components of a resistance bridge which, as the signal source, furnishes the voltage signals to the inputs of the circuit arrangement. As a result, the temperature dependence of the circuit arrangement can already be taken into account by appropriate selection of the resistances of the signal source, so that it is thus possible to achieve, without additional outlay, a complete circuit arrangement which contains the signal source as well as the differential voltage amplifier circuit arrangement, and has a temperature-independent characteristic curve.


REFERENCES:
patent: 3528022 (1970-09-01), Adams
patent: 4929907 (1990-05-01), Berkel
patent: 5404058 (1995-04-01), Nishijima
patent: 5471654 (1995-11-01), Okazaki et al.
patent: 5900782 (1999-05-01), Igarashi et al.

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