US-12620945-B2 - Electrical circuit

US12620945B2US 12620945 B2US12620945 B2US 12620945B2US-12620945-B2

Abstract

The invention relates to an electrical circuit in the form of a transimpedance amplifier stage, and to a method for operating this circuit. The invention furthermore relates to a circuit containing at least one signal amplifier that has at least one output connection, at least one input connection or at least one pair of differential input connections and at least two voltage supply connections, one of which may also be an earth or ground connection, wherein the signal amplifier has at least one additional connection that is connected internally to at least one of the input connections or the input connection via at least one further component, for example a diode.

Inventors

Ansgar Kirk
Stefan Zimmermann
Cornelius WENDT

Assignees

GOTTFRIED WILHELM LEIBNIZ UNIVERSITÄT HANNOVER

Dates

Publication Date: 20260505
Application Date: 20191009

Claims (13)

1 . An electrical circuit configured as a transimpedance amplifier stage, comprising: an input node, an output node, a feedback node, at least one signal amplifier comprising at least one output connection, and at least one input connection or at least one pair of differential input connections, wherein the an input signal applied to the at least one input connection or the at least one pair of differential input connections is converted into a multiple amplified output signal emitted at the at least one output connection, wherein the at least one output connection is connected or is connectable to the output node directly or via at least one further component, and wherein at least one of the at least one input connection or the at least one pair of differential input connections is connected to or is connectable to the input node directly or via at least one further component, wherein, in a case of an individual input connection of the at least one input connection a reference potential of a signal amplifier or, in a case of a pair of differential input connections of the at least one pair of differential input connections, the potential of an other input connection which is not connected or cannot be connected to the input node is a first reference potential, at least one feedback element connected to or connectable to the input node with a first connection directly or via at least one further component and to the feedback node with a second connection directly or via at least one further component, at least one feedback control element connected to or connectable to the feedback node with a first connection directly or via at least one further component and to the output node with a second connection directly or via at least one further component, at least one first switch through which the feedback node is connectable to a second reference potential directly or via at least one further component, at least one second switch through which the output node is connectable to the input node directly or via at least one further component, at least one current limiting component connected in series to the at least one second switch, wherein the at least one current limiting component has a current transfer characteristic through which substantially no current flows when a voltage applied to the at least one current limiting component is small, but in a case of a larger voltage, a current flows which is larger by more than a ratio of the voltage and the larger voltage, whereby the at least one current limiting component minimizes interference effects of the at least one first switch and/or the at least one second switch, wherein the at least one first switch and/or the at least one second switch are controllable by electrical control signals, wherein the electrical circuit has a control device for controlling the switching of the at least one first switch and/or the at least one second switch, wherein the control device is configured in a first operating mode for switching the at least one first switch and/or the at least one second switch into switching positions in which an input current flowing into the input node is converted into an amplified, integrated or other dependent output voltage signal at the output node of the electrical circuit, and wherein the control device is configured in a second operating mode for switching the at least one first switch and/or the at least one second switch to switching positions by which the feedback element is actively controlled to a neutral state, wherein the at least one signal amplifier compensates for voltage drops at the at least one first switch and/or the at least one second switch and other components located in a discharge path during the second operating mode by a high amplification factor of the at least one signal amplifier, and wherein the electrical circuit is operated in the first operating mode more than in the second operating mode.
2 . The electrical circuit as claimed in claim 1 , wherein the feedback control element is formed by a resistor, a capacitor, or a circuit arrangement made up of one or a plurality of resistors and/or one or a plurality of capacitors.
3 . An electrical circuit configured as a transimpedance amplifier stage, comprising: an input node, an output node, at least one signal amplifier which comprises at least one output connection and at least one input connection or at least one pair of differential input connections, wherein an input signal applied to the at least one input connection or the at least one pair of differential input connections is converted into a multiple amplified output signal emitted at the at least one output connection, wherein the at least one output connection is connected to or connectable to the output node directly or via at least one further component, and wherein the at least one input connection or the at least one pair of differential input connections is connected to or connectable to the input node directly or via at least one further component, wherein, in a case of an individual input connection of the at least one input connection a reference potential of a signal amplifier or, in a case of a pair of differential input connections of the at least one pair of differential input connections a potential of an other input connection which is not connected or cannot be connected to the input node is a first reference potential, at least one feedback element which is connected to or connectable to the input node with a first connection directly or via at least one further component, and is connected to or connectable to the output node with a second connection directly or via at least one further component, at least one further signal amplifier which comprises at least one further output connection and at least one further input connection or at least one further pair of differential input connections, wherein an input signal applied to the at least one further input connection is converted into a multiple amplified output signal emitted at the at least one further output connection, wherein the at least one further output connection is connected to a second switch directly or via at least one further component and at least one further input connection is connected to the output node directly or via at least one further component, wherein, in a case of an individual further input connection of the at least one further input connection, a reference potential of a further signal amplifier or, in a case of a further pair of differential input connections of the at least one pair of differential input connections, a potential of an other further input connection which is not connected or cannot be connected to the output node is referred to as a second reference potential, at least one second switch through which the further output connection is connectable to the input node directly or via at least one further component, at least one current limiting component connected in series to the at least one second switch, wherein the at least one current limiting component has a current transfer characteristic through which substantially no current flows when a voltage applied to the at least one current limiting component is small, but in a case of a larger voltage, a current flows which is larger by more than a ratio of the voltage and the larger voltage, whereby the at least one current limiting component minimizes interference effects of at least one first switch and/or the at least one second switch, wherein the at least one second switch is controllable by electrical control signals, wherein the electrical circuit has a control device for controlling the switching of the at least one second switch, wherein the control device is configured in a first operating mode for switching the at least one second switch into a switching position in which an input current flowing into the input node is converted into an amplified, integrated or other dependent output signal voltage at the output node of the electrical circuit, and wherein the control device is configured in a second operating mode for switching the at least one second switch to a switching position by which the feedback element is actively controlled to a neutral state, wherein the at least one signal amplifier compensates for voltage drops at the at least one second switch and other components located in a discharge path during the second operating mode by a high amplification factor of the at least one signal amplifier, and wherein the electrical circuit is operated in the first operating mode more than in the second operating mode.
4 . The electrical circuit as claimed in claim 3 wherein the second reference potential corresponds to the first reference potential.
5 . The electrical circuit as claimed in claim 1 , wherein the control device is set up to switch the first and the second switch in a same direction.
6 . The electrical circuit as claimed in claim 1 wherein the feedback control element is designed as a third switch which is switched by the control device in an opposite direction to the first switch, wherein the first and the third switch are designed as individual switches or as a common changeover switch.
7 . A method for operating a circuit as claimed in claim 1 wherein the feedback element is reset to a neutral state by actively regulating a voltage across the feedback element to a specific value.
8 . The method as claimed in claim 7 , wherein in a first operation mode of the electrical circuit, a current flowing into the input node is converted into an amplified, integrated or otherwise dependent output signal at the output node of the electrical circuit, and in a second operation mode of the electrical circuit, the electrical circuit is actively regulated to a neutral state, wherein the first and the second operation mode are switchable.
9 . The method as claimed in claim 7 wherein the feedback element is formed by a resistor, or a circuit arrangement made up of a plurality of resistors.
10 . The electrical circuit as claimed in claim 1 , wherein the at least one current limiting component is formed by input protection diodes integrated in a signal amplifier.
11 . The electrical circuit as claimed in claim 1 wherein the output node is coupled with a differentiator.
12 . The electrical circuit as claimed in claim 1 wherein the second reference potential corresponds to the first reference potential.
13 . The method as claimed in claim 7 wherein the feedback element is formed by a capacitor, or a circuit arrangement made up of a plurality of capacitors.

Description

The invention relates to an electrical circuit in the form of a transimpedance amplifier stage as well as to a method for operating this circuit. The invention additionally relates to a circuit with at least one signal amplifier which has at least one output connection, at least one input connection or at least one pair of differential input connections as well as at least two voltage supply connections, one of which can also be an earth or ground connection, wherein the signal amplifier has at least one additional connection which is connected internally via at least one further component, for example a diode, to at least one of the input connections or to the input connection. In general, the invention relates to the field of circuits for signal amplification of electrical signals. Transimpedance amplifiers (TIA) convert and amplify an input current into an output signal that depends on it, usually in the form of an output voltage. The key parameters of a transimpedance amplifier include the possible dynamic range of the input current, the bandwidth and the input current noise. Since the noise generally increases with the bandwidth, the construction of fast, low-noise transimpedance amplifiers requires a particularly low noise. Transimpedance amplifiers are usually realized in a resistive, logarithmic or more rarely capacitive manner. Resistive transimpedance amplifiers possess an ohmic resistor as a feedback element. In order to reduce the input current noise, the resistance must be increased. A low-noise, resistive transimpedance amplifier therefore possesses a large feedback resistor, which for a wide dynamic range means that large output voltage amplitudes of several hundred volts must be driven. The resulting complexity in terms of circuitry is, therefore, impractical. Logarithmic transimpedance amplifiers use a diode or a bipolar transistor as a feedback element and thus compress the output signal. This circumvents the necessity for large output voltage amplitudes. However, the strong temperature dependence of the feedback properties of the semiconductor components and the relatively large leakage currents which limit the input current range downward prove to be disadvantageous in this case. Capacitive transimpedance amplifiers possess a capacitor as a feedback element. The output voltage corresponds to the integral of the input current over time. Owing to the very large insulation resistance of the capacitor, it adds practically no noise, unlike the ohmic resistor of the resistive transimpedance amplifier. At the same time, the output voltage amplitude is limited by the integration duration, eliminating the need for an expensive high-voltage supply for a low-noise transimpedance amplifier. In addition, the temperature dependence is comparatively low in comparison to the logarithmic transimpedance amplifier. The capacitive transimpedance amplifier architecture is therefore best suited for a low-noise amplifier with an extremely high dynamic range with currents from several fA up to several μA. In addition to the properties of the integration capacitor, the reset circuit for discharging the integration capacitor is essential for a high-performance transimpedance amplifier. This should ideally not affect the input path of the transimpedance amplifier. Leakage currents also flow through open switching elements and are often highly temperature dependent. Consequently, they cannot be compensated trivially and therefore substantially reduce the input current range. Charge injection results from parasitic capacitances in the switching element which switch charge to the input path when opening or closing the switching element and thus cause parasitic input currents and may even possibly saturate the integration capacitor. In addition, closed switching elements have a resistance greater than zero and, as a result of this, hinder the current flow and thus rapid discharge. Since relays are very inert, semiconductor-based analog switches which, however, have higher leakage currents, are generally used as switching elements. Switching elements today additionally all have charge injection. For these reasons, they cannot be used as a switching element for resetting the integration capacitor for input currents below 100 fA, which is why existing capacitive transimpedance amplifier designs have comparatively poor performance data. A circuit with a capacitive transimpedance amplifier is known from U.S. Pat. No. 9,324,546 B2. The underlying object of the invention is to specify an electrical circuit in the form of a transimpedance amplifier stage with improved operational data and a method for operating a circuit of this type. Furthermore, an improved circuit with at least one signal amplifier of the type mentioned at the outset shall be specified. This object is achieved by an electrical circuit in the form of a transimpedance amplifier stage, wherein the circuit has an input node, an output node and a feedback node,