Amplifiers – With semiconductor amplifying device – Including push-pull amplifier
Reexamination Certificate
2001-12-11
2003-05-06
Mottola, Steven J. (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including push-pull amplifier
C330S051000
Reexamination Certificate
active
06559721
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a circuit configuration with an integrated amplifier.
For example, it is common in sensor technology to capture a measuring signal in a remote sensor, amplify it and transmit it over a transmission line to evaluating electronics, which can be centrally disposed. It is also customary therein for the sensor to receive its operating voltage from the central unit, likewise over lines.
It may be desirable, for instance for reasons of operational reliability, to be able to detect an interruption of a supply line from the central unit to the remote sensor with the aid of the measuring signal, for instance in the central unit. Otherwise, given an error in the supplying of the sensor, it could provide a signal that could be misinterpreted as a measured signal.
A known technique given an interruption, for instance a break of a supply line, is to create a low-impedance connection from the output terminal of the sensor, which can provide a measuring signal, to the supply voltage terminals at the sensor. Thus, in the central unit it is possible to detect a failure in that the potential of the output signal is above an upper potential limit or below a lower potential limit that typically occur in normal operation.
Published, Non-Prosecuted German Patent Application DE 44 00 437 A1 describes a semiconductor sensor device. There, given an interruption of a voltage supply terminal, a value outside a predefined range is outputted at the output by a clipper.
2. Summary of the Invention
It is accordingly an object of the invention to provide a circuit configuration with an integrated amplifier which overcomes the above-mentioned disadvantages of the prior art devices of this general type, which makes possible, in a simple and reliable fashion, the detection of a failure such as an interruption of a supply voltage supplying the circuit configuration.
With the foregoing and other objects in view there is provided, in accordance with the invention, a circuit configuration. The circuit has an integrated amplifier with a symmetrical amplifier output, a supply potential terminal to be coupled to a voltage source for supplying an operating current, a reference potential terminal to be coupled to the voltage source, a tri-state output, and an output stage having a pair of complementary output transistors with control inputs connected to the symmetrical amplifier output. The pair of complementary output transistors includes a first output transistor having a controlled path coupling the supply potential terminal to the tri-state output, and a second output transistor having a controlled path coupling the tri-state output to the reference potential terminal. The output stage further has switches coupling the first and second output transistors with the tri-state output so that the tri-state output is put into a high-impedance state given an interruption of the operating current.
To couple the output transistors with the tri-state output, a blocking circuit can be provided, which is driven by a driver circuit, which is connected to the reference and supply potential terminals for its current supply. During normal operation, the blocking circuit can effectuate a low-impedance coupling of the output transistors with the tri-state output. But if a disturbance such as an interruption of the current supply occurs, then a high-impedance coupling of the output transistors with the tri-state output is effectuated with the aid of the driver circuit.
The input of the amplifier can be connected to the output of a sensor.
The circuit configuration can be coupled with a voltage source, which can be connected by lines.
The amplifier output can be laid out symmetrically, i.e. for conducting a difference signal. Such a difference signal is customarily carried on two lines.
During normal operation of the circuit configuration, the output stage at the tri-state output can provide a digital signal or an analog signal at its output, depending on the signal on the input side, for instance the measuring signals of a sensor. The digital signal can be a binary signal, which can have two states, low and high. The logic states are customarily coded by respective voltage values or voltage ranges.
In the normal operation of the circuit configuration, the signal levels that can arise are within a defined range, which can have lower and upper limits.
The normal operation of the circuit configuration is interrupted by the interruption of the operating-current supply, for example. In this case, in the described circuit configuration the tri-state output is put into a high-impedance state. This can be easily detected in that the signal available at the tri-state output, with respect to its voltage level or potential, is above an upper voltage or below a lower voltage occurring in normal operation. In order to accomplish this, a load resistance can be connected to the tri-state output. The load resistance can be connected to the tri-state output via one terminal and to a reference or supply potential terminal via another terminal. This is of course predicated on the condition that the tri-state output has a substantially higher-impedance than the load resistance connected to it.
If the load resistance is connected to the reference potential terminal with its additional terminal, it draws the tri-state output to the reference potential given an interruption of the operating-current supply. The load instance can be referred to as a pull-down load instance. If, on the other hand, the load resistance is connected between the supply potential terminal and the tri-state output, then given an interruption of the operating-current supply of the circuit configuration, the tri-state output is drawn to the supply potential.
The described circuit configuration is well suited to integration in an integrated circuit. In an integrated circuit, the amplifier and the sensor that is connected to the amplifier on the input side can be integrated, as can the output stage. The voltage source for supplying the circuit configuration can be disposed in a central unit, in which the load resistance can also be provided. Furthermore, a converting and evaluating circuit can also be provided in the central unit, which, in a normal operation of the circuit, continually compares the potential at the tri-state output of the output stage to an upper and lower limit, and emits a signal indicating a disturbance when a limit is crossed.
The described circuit configuration has a number of advantages over a circuit configuration whose output stage provides a low-impedance output given the interruption of an operating-current supply of the circuit. Self-conducting transistor structures are usually required therein, which are not provided in the majority of known manufacturing processes for semiconductor circuits and therefore require additional implantation steps. In contrast, in the present circuit configuration, self-blocking transistors can be utilized in the output stage, which are usually present in BiCMOS or CMOS processes.
In the event of a failure, a high-impedance output of the output stage makes it possible to better differentiate a failure state from the normal operating state. Furthermore, self-blocking transistors do not lead to a transient pulse when the circuit configuration is powered up. Beyond this, the current consumption of the circuit in the event of failure is relatively small.
When the load resistance is interposed between the supply potential terminal and the tri-state output, the potential at the tri-state output is equal to the supply potential given the interruption either of the line connecting the voltage source and the supply potential terminal or of the line connecting the reference potential terminal and the supply voltage source, or when both lines are interrupted. If, on the other hand, the load resistance is connected between the tri-state output and the reference potential terminal, then the potential at the tri-state output is equal to the reference potent
Ausserlechner Udo
Motz Mario
Greenberg Laurence A.
Infineon - Technologies AG
Maybeck Gregory L.
Mottola Steven J.
Stemer Werner H.
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