Output circuit for electronic circuit for transmitting analog output signal

Abstract

The invention relates to an output circuit for an electronic circuit for outputting an analog output signal, comprising:-a first and a third electronic switch (M1, M2); a fourth electronic switch (M4) and a fifth electronic switch (M5); an operational amplifier (O1), which receives the control signal at the non-inverting input, the output of which is connected via a first resistor (R1) to the control input of the first electronic switch (M1) and via a fifth electronic switch (M5) to the first output connection of the output circuit (1), the inverting input end of the operational amplifier is connected with the power supply potential through a second resistor (R2); -wherein a current-carrying path of the first electronic switch (M1) connects the first output connection (A1) to the inverting input of the operational amplifier (O1),-wherein a fourth electronic switch (M4) connects the inverting input of the operational amplifier (O1) to the second output connection (A2); -wherein a third electronic switch (M3) connects the second output connection to the supply potential.

Description

Technical Field

[0001] The present invention relates to an output circuit for an electronic circuit that outputs an analog output signal according to different signal transmission types. The present invention also relates to a configurable output circuit that can be used to operate according to different signal transmission types. Background Art

[0002] Electronic circuits in devices for signal transmission of analog signals (e.g. from measuring transducers) in process automation usually use uniform and standardized output signals to transmit measurement signals, etc. For analog signal transmission, the devices usually provide standard signals for this purpose, such as a 4mA to 20mA current interface or a 0V to 10V voltage interface. In addition, the output circuit can also be operated as a current sink, wherein the output circuit provides an impedance (ohmic resistance) that depends on the analog signal to be output. All types of signal transmission are based on the provided analog voltage signal.

[0003] Here, different signal transmission types as voltage-controlled voltage source, voltage-controlled current source or current sink have different advantages, so that a wide range of application cases can be covered. Therefore, for a device that can be used in different environments, it is advantageous if the output circuit is capable of each of the above-mentioned signal transmission types, so that the device can be easily adapted to the corresponding application.

[0004] So far, a corresponding separate output circuit and / or additional output connections adapted individually to the signal transmission type have been provided for each signal transmission type. The electronics of the output circuits or parts of the output circuits predetermined for the remaining unused signal transmission types remain passive and only increase the costs for providing the entire device electronics, especially if multiple channels are required for analog output signals. In addition, previous solutions provide different output terminals for each type of analog output signal depending on the signal transmission type, which increases the wiring workload and the possibility of errors when connecting the device.

[0005] It is therefore an object of the present invention to provide an improved output circuit for outputting analog signals in different signal transmission types, which can be designed in an efficient manner, in particular using fewer components. Summary of the invention

[0006] This object is achieved by an output circuit for providing multiple signal transmission types according to the present invention.

[0007] Other embodiments are given in the examples.

[0008] According to a first aspect, an output circuit for an electronic circuit of a device outputting an analog output signal in one of a plurality of signal transmission types is proposed, the output circuit comprising:

[0009] - a first electronic switch and a third electronic switch, each having a control input;

[0010] a first standard or Schottky diode or a fourth electronic switch with a corresponding control input;

[0011] - a fifth electronic switch or a second standard or Schottky diode,

[0012] - Operational amplifier,

[0013] ○The operational amplifier receives a control signal at the non-inverting input terminal representing the output signal to be output,

[0014] The output of the operational amplifier is connected to the control input of the first electronic switch via the first resistor, in particular directly;

[0015] The output of the operational amplifier is also connected to the first output terminal of the output circuit via a fifth electronic switch or a second standard or Schottky diode, and

[0016] The inverting input of the operational amplifier is connected to the power supply potential, in particular directly, via a second resistor;

[0017] wherein the current-carrying path of the first electronic switch connects the first output terminal, in particular directly, to the inverting input of the operational amplifier,

[0018] - wherein a fourth electronic switch or a first standard or Schottky diode connects the inverting input of the operational amplifier to the second output terminal;

[0019] - wherein the third electronic switch connects the second output terminal to the supply potential.

[0020] The output circuit for outputting the analog output signal comprises an operational amplifier connected in different ways by means of a plurality of electronic switches (such as MOSFET transistors, etc.) to output the analog output signal. The electronic switches can be configured so that the operational amplifier can be switched in various basic circuits according to the desired signal transmission type. Thus, depending on the switching mode of the electronic switches, the operational amplifier can operate as a voltage-controlled current source and / or as a voltage-controlled current sink and / or a voltage-controlled voltage source.

[0021] Regardless of the selected signal transmission type, the output circuit can provide output signals at two output terminals. Overall, using only one operational amplifier and multiple electronic switches reduces the number of necessary components compared to an output interface that provides a separate output circuit for each signal transmission type.

[0022] In addition, since redundancy is avoided, power consumption in circuit design can be reduced and space can be saved. In addition, interference effects caused by passive circuit parts will not be generated, and corresponding compensation measures for eliminating interference can be omitted.

[0023] One idea of ​​the above output circuit is to set up an operational amplifier to realize all signal transmission types. The operational amplifier is supplied with a power supply voltage by connecting to a high power supply potential and a low power supply potential.

[0024] The control signal is applied to the non-inverting input of the operational amplifier in the form of a variable voltage whose level corresponds to the analog value of the output signal. The input signal may correspond to a voltage within a voltage range between a high power supply potential and a low power supply potential of the operational amplifier.

[0025] A first electronic switch is provided, which is connected between a first output terminal of the output circuit and an inverting input of the operational amplifier, in particular directly or via another electrical or electronic component, in particular via a current limiting resistor. A control terminal of the electronic switch is connected to the output of the operational amplifier via a first resistor.

[0026] A direct (electrical) connection is understood here as a conductive, very low-resistance electrical connection, such as a connection produced by a conductor track or conductor connection, i.e., without intermediate electrical or electronic components. In a broader sense, a direct connection can be understood here as an electrical connection that does not include functionally effective components.

[0027] The second electronic switch can be arranged in series with the second resistor.The inverting input of the operational amplifier is thus connected to the low supply potential, in particular directly via the second resistor and the second electronic switch.

[0028] The second output terminal of the output circuit is connected to the low supply potential, in particular directly via the third electronic switch.

[0029] The inverting input of the operational amplifier is also connected to the second output terminal, in particular directly or via further electrical or electronic components (for example by means of a high-resistance resistor directly at the inverting input of the operational amplifier), via a fourth electronic switch or a first standard or Schottky diode.

[0030] The output of the operational amplifier can be connected via a fifth electronic switch or a second standard or Schottky diode, in particular directly, to the first output terminal of the output circuit.

[0031] The electronic switch can be implemented, for example, with a MOSFET transistor which can be digitally controlled at its control input with a high or low level. The exception is the first electronic switch which, in the signal transmission type of a current sink, adjusts the voltage across the series connection of the second resistor and the second electronic switch by means of a variable resistance of the first electronic switch.

[0032] This construction makes it possible to determine the type of signal transmission of the output circuit by selecting the control of the electronic switch. The core here is an operational amplifier, which is controlled at the non-inverting input with a control signal, which corresponds to or specifies the analog output signal to be output and represents the rated value of the analog output signal. The output of the operational amplifier can obtain negative feedback via the inverting input of the operational amplifier, thereby forming a control loop of the voltage-controlled voltage source.

[0033] If the output circuit is to be operated as a voltage-controlled voltage source, the second and fourth electronic switches or the first standard or Schottky diode are switched to high resistance (off), and the first and third electronic switches (and the fifth electronic switch, if present) are switched to low resistance (on). Thus, the basic circuit of a voltage follower is formed by the load resistor at the output (between the output terminals), so that the voltage at the first output terminal substantially corresponds to the voltage of the control signal.

[0034] In contrast, if the output circuit is to be operated as a voltage-controlled current source, the first and third electronic switches are switched to high resistance, and the second and fourth electronic switches or the first standard or Schottky diode (and the fifth electronic switch, if present) are switched to low resistance (conducting). The current from the output of the operational amplifier now flows through the fifth electronic switch or the second diode, through the load applied to the output terminal through the fourth electronic switch or the first standard or Schottky diode, and across the series connection of the second resistor and the second electronic switch a voltage drop is generated, which should correspond to the voltage of the control signal in the regulated state. The voltage of the control signal thus causes the operational amplifier to increase the current until the same voltage appears at the input of the operational amplifier. This corresponds to the basic circuit of a voltage-controlled current source.

[0035] As another type of signal transmission, the output circuit can be operated as a current sink, where the applied load corresponds to the load impedance with an additional external load voltage source. A current sink is formed between the output terminals by the output circuit. The second electronic switch is switched to a low resistance, and the fourth electronic switch or the first standard or Schottky diode (and the fifth electronic switch, if present) is switched to a high resistance, so that the current now flows through the first electronic switch and the series connection of the second resistor and the second electronic switch. The circuit is closed by switching the third electronic switch to a low resistance. Here, the voltage drop across the series connection of the second resistor and the second electronic switch should also correspond to a voltage equal to the control signal. The operational amplifier adjusts the voltage across the series connection of the second resistor and the second electronic switch by means of the variable resistance of the first electronic switch. To this end, the control terminal of the first electronic switch is switched to a high resistance so that the output of the operational amplifier alone can control the voltage of the control input of the first electronic switch.

[0036] Here, the fifth electronic switch switched to high resistance or the second diode in reverse disconnects the external voltage source from the output of the operational amplifier. Here, the load current flowing through the load impedance corresponds exactly to the current flowing through the second resistor, since no current can be absorbed by the operational amplifier on the output side. The first electronic switch acts as a variable resistor controlled by the operational amplifier.

[0037] The polarity remains the same for all signal transmission types of the output circuit, so that switching between signal transmission types is possible without adjusting the wiring. The different signal transmission types are controlled, for example, by mechanical switches, such as DIP switches, microcontrollers or any other switching logic.

[0038] In the case of light loads and high output currents, high power losses can result if the supply voltage of the op amp is designed for the maximum allowed load. The high power losses in the op amp are caused by the high voltage difference between the supply voltage and the output voltage of the op amp.

[0039] Therefore, in order to reduce power losses, the supply voltage of the operational amplifier can be adapted to the resistance of the applied load. Various circuits can be envisaged for this purpose. For example, the output voltage of the operational amplifier can be read using an ADC converter and the supply voltage can be reduced to a level slightly higher than the output voltage (but only until the output voltage is not pinched off).

[0040] In particular, the fourth electronic switch can be formed by two MOSFETs arranged in series and polarized oppositely with respect to the current carrying path to ensure reverse polarity protection. Thus, reverse polarity protection can be ensured when the output circuit is operated as a current sink and an additional load voltage source is used as a load.

[0041] Reverse polarity protection ensures that the circuit is not damaged in the event of reverse polarity and that the externally connected load voltage source does not provide an "unlimited" or unregulated current. Without reverse polarity protection, in the event of reverse polarity, the current would flow through the body diode of the electronic switch, which is designed as a MOSFET, for example. This would therefore result in a series connection of the external load with the two diodes, resulting in a resultant high current.

[0042] In another embodiment, a fuse can be arranged in series with the first output terminal so as to interrupt the circuit in the event of a fault with an impermissibly high current. Considering the intrinsic safety of the circuit, a current-limiting output resistor can also be used instead of a fuse.

[0043] A possibility to save even more components is to omit the second electronic switch and to provide only the second resistor as a connection between the inverting input of the operational amplifier and the second supply potential. As a result, in the type of signal transmission of the voltage-controlled voltage source, a large amount of current flows through the second resistor R2, since in this case the output voltage is present substantially directly across the second resistor. This change is at the expense of power losses, which now occur in the second resistor and must be provided by the operational amplifier.

[0044] In the signal transmission type of the voltage-controlled voltage source, a third resistor may be connected in series with the first electronic switch. The output voltage of the output circuit then corresponds to the voltage of the output signal to be output multiplied by a factor (R3: resistance value of the third resistor, R2: resistance value of the second resistor).

[0045] The control element can be arranged to manipulate the control input of the electronic switch according to the signal transmission type to be configured. In particular, the control element can be designed to manipulate the first electronic switch, the third electronic switch and possibly the fifth electronic switch to be turned on, and manipulate possibly the second electronic switch and the fourth electronic switch to be turned off, when the signal transmission type of the voltage-controlled voltage source is to be adjusted. In an alternative case, the first standard or Schottky diode is turned off.

[0046] According to one embodiment, the control element can be designed to control the first and third electronic switches to be turned off and control the possible second electronic switch, the possible fourth electronic switch and the possible fifth electronic switch to be turned on when the signal transmission type of the voltage-controlled current source is to be adjusted. In an alternative case, the first standard or Schottky diode is turned on.

[0047] According to one embodiment, the control element can be designed to: switch the first electronic switch so that the first electronic switch is controlled by the voltage at the output of the operational amplifier; control the possible second electronic switch and the third electronic switch to be turned on; and control the fourth electronic switch and the possible fifth electronic switch to be turned off when the signal transmission type of the voltage-controlled current sink is adjusted.

[0048] According to one embodiment, the control element can be designed to confirm the configuration of the voltage-controlled current sink as a signal transmission type by means of a voltage measuring unit at the inverting input of the operational amplifier in the following manner:

[0049] - operating the first electronic switch, the third electronic switch and possibly the second electronic switch to a low resistance state, and operating the possible fourth electronic switch and possibly the fifth electronic switch to a high resistance state, while setting the voltage of the non-inverting input terminal of the operational amplifier to 0 V, provided that: the voltage measured at the inverting input terminal of the operational amplifier is not equal to 0 V.

[0050] In addition, the control element can be designed to switch the possible second electronic switch and the possible fifth electronic switch and the possible fourth electronic switch to a low resistance state, and switch the first electronic switch and the third electronic switch to a high resistance state, and apply a voltage not equal to 0V to the non-inverting input terminal of the operational amplifier, wherein, if the voltage measured at the inverting input terminal of the operational amplifier is not equal to the voltage at the non-inverting input terminal of the operational amplifier, the voltage-controlled voltage source is configured as a signal transmission type, otherwise the voltage-controlled current source is configured as a signal transmission type.

[0051] A current limiting resistor may be arranged between the fifth electronic switch or the second diode and the first output terminal.

[0052] A third resistor may be arranged in series with the first electronic switch. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Embodiments are explained in detail below with the aid of the accompanying drawings. In the drawings:

[0054] Figure 1 A circuit diagram showing an output circuit according to an embodiment;

[0055] Figure 2 A diagram showing the active current path when operating with a voltage controlled voltage source as the signal transmission type;

[0056] Figure 3 A diagram showing an active current path when operating in a signal transmission type of voltage controlled current source; and

[0057] Figure 4A diagram showing the current path when operating in the signal transmission type of current sink;

[0058] Figure 5 shows a circuit diagram of another embodiment with other optional supplements; and

[0059] Figure 6 A flow chart illustrating a method for operating an output circuit is shown. DETAILED DESCRIPTION

[0060] Figure 1 The circuit diagram of the output circuit 1 is shown, which can operate in three signal transmission types. The core of the output circuit 1 is an operational amplifier O1. The power supply voltage U across the first power supply potential (especially high power supply potential) VH and the second power supply potential (especially low power supply potential) VL is vers Supply power to operational amplifier O1.

[0061] Apply a control signal V to the non-inverting input of the operational amplifier O1. ref .

[0062] The output of the operational amplifier is connected to the control input of the first electronic switch M1, in particular directly via the first resistor R1. The first electronic switch M1 connects the first output terminal A1, in particular directly, to the inverting input of the operational amplifier O1 with its current-carrying path. The first electronic switch can be designed, for example, as a MOSFET and can be switched to a conducting state, switched to a non-conducting state and can be variably controlled in a manner known per se by applying a corresponding control voltage to adjust the adjustable resistance.

[0063] The inverting input terminal of the operational amplifier O1 is connected to the second power supply potential via the second resistor R2. Optionally, the second electronic switch M2 can be arranged in series with the second resistor R2. The second electronic switch M2 can also be designed as a MOSFET transistor. The second electronic switch M2 can prevent a large current from flowing through the second resistor R2 under the signal transmission type of the voltage-controlled voltage source.

[0064] The second output terminal A2 is connected to the second supply potential VL, in particular directly, via a third electronic switch M3 (which can also be designed as a MOSFET transistor). In addition, the second output terminal A2 is connected to the inverting input of the operational amplifier O1, in particular directly, via a fourth electronic switch M4. The fourth electronic switch M4 can include a MOSFET transistor, or alternatively can be designed as a series connection of two MOSFET transistors with reverse polarity, in order to achieve reverse polarity protection for the output circuit in the case of a signal transmission type of a current sink.

[0065] Alternatively, the fourth electronic switch can be replaced by a first standard or Schottky diode D1 which is connected between the second output terminal A2 and the inverting input of the operational amplifier O1 , in particular directly in the forward direction.

[0066] In addition, the fifth electronic switch M5 can be arranged between the output of the operational amplifier O1 and the first output terminal A1. The fifth electronic switch M5 can also be designed with a MOSFET transistor. Alternatively, the fifth electronic switch M5 can also be replaced by a second diode D2. In the signal transmission type operation of the current sink, the second diode is cut off.

[0067] In order to select the type of signal transmission by means of which the output signal should be output via the output terminals A1, A2, the electronic switches M1-M5 can be controlled in a targeted manner with suitable configuration signals G1-G5 so as to switch them to be conductive or non-conductive. It is also proposed for the first electronic switch M1 that it is operated as an adjustable resistor so that it is adapted in the control loop of the operational amplifier to the current flowing through the second resistor R2.

[0068] The electronic switches M1 - M5 can be actuated by means of a control element 10 , which can be designed, for example, in the form of a mechanical switch (eg a DIP switch).

[0069] The control element 10 can also be designed as a control circuit, which provides configuration signals G1-G5 for the corresponding electronic switches M1-M5 according to the specification. The control element 10 can also include the following functions: based on the load impedance and load voltage present at the output terminal, the required signal transmission type is identified and the signal transmission type is automatically set in the output circuit. The method is explained below.

[0070] Figure 2 The current paths for operating the output circuit 1 as a voltage-controlled voltage source are shown. If the output circuit is operated in the signal transmission type of the voltage-controlled voltage source, the first electronic switch M1 and the third electronic switch M3 are switched to low resistance or on, while the optional second electronic switch M2 and the fourth electronic switch M4 are switched to high resistance or off. In the alternative case where a first standard or Schottky diode is present instead of the fourth electronic switch M4, this diode is off. Whenever present, the fifth electronic switch M5 is also switched on. The basic circuit of a voltage follower is created by the load resistor between the output terminals A1, A2, so that the voltage between the output terminals A1, A2 corresponds to the voltage V of the output signal to be applied. ref .

[0071] In the case of low load impedance and high output current, if the supply voltage of the operational amplifier O1 is designed for the maximum allowed load, high power losses will result. To reduce power losses, the circuit can also be extended with an additional supply voltage tracking device. The supply voltage tracking device can read the output voltage of the operational amplifier using an ADC converter and reduce the supply voltage to slightly above the output voltage so that the output voltage is just not clipped.

[0072] Figure 3 The active current path is shown when the output circuit is switched to a voltage-controlled current source. If the output circuit operates in the signal transmission type of a voltage-controlled current source, the first electronic switch M1 and the third electronic switch M3 are switched to high resistance or non-conducting, while the optional second electronic switch M2 and the fourth electronic switch M4 are switched to low resistance or conducting. In the alternative case where there is a first standard or Schottky diode D1 instead of the fourth electronic switch M4, the diode is conducting. Whenever present, the fifth electronic switch M5 is also switched to conducting.

[0073] The current from the output terminal of the operational amplifier O1 is transmitted through the fifth electronic switch M5 / the second diode D2, through the load impedance R last and flows back through the fourth electronic switch M4 and generates a voltage drop across the second resistor R2 and the optional second electronic switch M2, which should correspond to the voltage V of the control signal in a stable state. ref .

[0074] Therefore, the voltage of the control signal V ref This causes the operational amplifier O1 to increase its current until the same voltage appears at its inverting input. This corresponds to the basic circuit of a voltage-controlled current source.

[0075] Figure 4 The current carrying path when operating in the signal transmission type of a current sink is schematically shown. If the output circuit 1 operates as a current sink, the load impedance R last The external load voltage source V in series ext Here, the fourth electronic switch M4 and the fifth electronic switch M5 are switched off, while the second electronic switch M2 and the third electronic switch M3 are switched on. In the alternative case where there is a first standard or Schottky diode D1 instead of the fourth electronic switch M4, this diode is blocked.

[0076] The first electronic switch M1 is variably controlled by the output of the operational amplifier O1, thereby adjusting the resistance through the current carrying path of the first electronic switch M1, so that the voltage drop across the second resistor R2 corresponds to the voltage V of the control signal refTherefore, the control terminal of the first electronic switch M1 needs three states, namely: high level, low level and high resistance, so as to achieve variable control when operating as a current sink.

[0077] For different signal transmission types, the following manipulation results are produced:

[0078] Signal transmission type G1 G2 G3 G4 G5 Voltage Controlled Voltage Source Conductivity Deadline Conductivity Deadline Conductivity Voltage Controlled Current Source Deadline Conductivity Deadline Conductivity Conductivity Current Sink High resistance Conductivity Conductivity Deadline Deadline

[0079] Figure 5 Circuit diagrams showing other embodiments of output circuits.

[0080] The fifth electronic switch M5 switches the external load voltage source V ext Instead of the fifth electronic switch M5, a second diode D2 may be provided alternatively or additionally, the second diode representing an active current path in the signal transmission type of the voltage-controlled voltage source and the voltage-controlled current source, and when the output circuit operates in the signal transmission type of the current sink, the second diode is cut off so as to connect the output terminal of the operational amplifier O1 to the external load voltage source V ext Decoupling.

[0081] In addition to the fourth electronic switch M4, another sixth electronic switch M6 of opposite polarity may be provided, which is designed as a MOSFET of opposite polarity, thereby allowing an external load voltage source V to be used in a current sink signal transmission type. ext Reverse.

[0082] Alternatively or additionally, a fuse or current limiting resistor R ex It may be arranged in series with the first output terminal A1 in order to interrupt the circuit or limit the current in the event of a fault with an inadmissibly high current.

[0083] The second electronic switch M2 is optional and can therefore be omitted, and instead only the second resistor R2 can be used. This means, however, that for the type of signal transmission of a voltage-controlled voltage source, a large amount of current flows through the second resistor R2, since in this case the output voltage is also directly present across R2. However, this variation comes at the expense of power losses, which occur in the second resistor R2 and must be provided by the operational amplifier O1.

[0084] Provides control signal voltage V ref The required reduction of the voltage fluctuation can be achieved by providing a third resistor R3 in series with the first electronic switch M1. This forms the basic circuit of a non-inverting amplifier, in which the output voltage at the output of the operational amplifier O1 corresponds to the voltage of the control signal multiplied by a factor

[0085] The output circuit can be automatically configured by means of the control element 10. Corresponding to the identified signal transmission type, the corresponding configuration signals G1-G5 are set according to the above table.

[0086] A voltage measuring unit 11, such as an analog-to-digital converter (ADC), is required at the inverting input of the operational amplifier O1, so that automatic recognition of the operating mode can be achieved.

[0087] By systematically manipulating the switches based on the two switch combinations, the current configuration can be identified. Figure 6 The method steps are shown in the flowchart of FIG.

[0088] First, in step S1, the first electronic switch, the second electronic switch and the third electronic switch are switched to low resistance, while the fourth electronic switch M4 and the fifth electronic switch M5 are kept at high resistance. ref Set to 0V.

[0089] In step S2 , it is checked whether the voltage value of 0 V is not present at the inverting input terminal of the operational amplifier O1 during voltage measurement.

[0090] If this is not the case (option: No), the method continues to step S3. Otherwise (option: Yes), i.e. the voltage value 0 V is different from the voltage at the inverting input of the operational amplifier O1, the signal transmission type is the mode of voltage-controlled current sink and the configuration signal is set accordingly. Here, the switching on of switches M1 and M2 has caused a current flow so that the measured voltage is equal to the voltage V of the output signal. ref No. In contrast, if no current flows, then a voltage-controlled current source or voltage source type of signal transfer can be assumed.

[0091] In step S3, the second electronic switch M2 and possibly the fourth electronic switch M4 are switched to low resistance, and the first electronic switch M1 and the third electronic switch M3 are switched to high resistance. Now, the voltage V of the output signal is set ref , which should generate a few mA of current through a low resistance load.

[0092] In step S4, it is checked whether the set voltage value is inconsistent with the voltage value measured at the inverting input terminal of the operational amplifier O1.

[0093] If this is not the case (option: No), the signal transmission type is voltage-controlled current source mode and the configuration signals are set accordingly. Otherwise (option: Yes), the signal transmission type is voltage-controlled voltage source mode and the configuration signals are set accordingly. If the voltage measurement shows that the voltage V of the output signal is not reached ref, we can conclude that a very high resistance load is connected, which is a characteristic of a voltage-controlled voltage source. The reason is that the operating voltage of the operational amplifier O1 is not enough to drive the corresponding current. Therefore, it is a voltage-controlled voltage source.

Claims

1. An output circuit (1) for outputting an analog output signal in one of a plurality of signal transmission types for an electronic circuit of a device, the output circuit comprising: - a first electronic switch and a third electronic switch (M1, M2), each of which has a control input terminal; - a first standard or Schottky diode (D1) or a fourth electronic switch (M4) with a corresponding control input; - a fifth electronic switch (M5) or a second standard or Schottky diode (D2), - Operational amplifier (O1), ○ The operational amplifier receives a control signal representing an output signal to be output at a non-inverting input terminal, The output terminal of the operational amplifier is directly connected to the control input terminal of the first electronic switch (M1) via a first resistor (R1); The output of the operational amplifier is also connected to the first output terminal of the output circuit (1) via the fifth electronic switch (M5) or the second standard or Schottky diode (D2), in particular directly, and The inverting input of the operational amplifier is connected to the power supply potential, in particular directly, via a second resistor (R2); - wherein the current-carrying path of the first electronic switch (M1) connects the first output terminal (A1) to the inverting input of the operational amplifier (O1), in particular directly, wherein the fourth electronic switch (M4) or the first standard or Schottky diode (D1) connects the inverting input of the operational amplifier (O1) to the second output terminal (A2), in particular directly; - wherein the third electronic switch (M3) connects the second output terminal to the supply potential, in particular directly.

2. The output circuit (1) according to claim 1, wherein: A second electronic switch (M2) is arranged in series with the second resistor (R2).

3. The output circuit (1) according to claim 1 or 2, wherein: The adjustable signal transmission rate corresponds to a voltage-controlled voltage source, a voltage-controlled current source, and a voltage-controlled current sink.

4. The output circuit (1) according to any one of claims 1 to 3, wherein: A control element (10) is provided to actuate the control inputs of the electronic switches (M1-M5) according to the type of signal transmission to be configured.

5. The output circuit (1) according to claim 4, wherein: The control element (10) is designed to control the first electronic switch, the third electronic switch (M3) and the possible fifth electronic switch (M5) to be turned on, and control the possible second electronic switch and the possible fourth electronic switch (M2, M4) to be turned off when the signal transmission type of the voltage-controlled voltage source is adjusted.

6. The output circuit (1) according to claim 4 or 5, wherein: The control element (10) is designed to control the first electronic switch and the third electronic switch to be turned off, and control the possible second electronic switch (M2), the possible fourth electronic switch (M4) and the possible fifth electronic switch (M5) to be turned on when the signal transmission type of the voltage-controlled current source is to be adjusted.

7. The output circuit (1) according to any one of claims 4 to 6, wherein: The control element is designed to: switch the first electronic switch (M1) so that the first electronic switch is controlled by the voltage at the output end of the operational amplifier; control the possible second electronic switch (M2) and the possible third electronic switch (M3) to be turned on; and control the possible fourth electronic switch (M4) and the possible fifth electronic switch (M5) to be turned off when the signal transmission type of the voltage-controlled current sink is to be adjusted.

8. The output circuit (1) according to any one of claims 4 to 7, wherein: The control element (10) is designed to confirm, by means of a voltage measuring unit (11) at the inverting input of the operational amplifier (O1), that the voltage-controlled current sink is configured as a signal transmission type in the following manner: - operating the first electronic switch (M1), the third electronic switch (M3) and possibly the second electronic switch (M2) to a low resistance state, and operating the possible fourth electronic switch (M4) and possibly the fifth electronic switch (M5) to a high resistance state, while setting the voltage at the non-inverting input terminal of the operational amplifier (O1) to 0V, provided that the voltage measured at the inverting input terminal of the operational amplifier (O1) is not equal to 0V.

9. The output circuit (1) according to claim 8, wherein: The control element (10) is designed to switch the possible second electronic switch (M2) and the possible fourth electronic switch (M4) to a low resistance state, and to switch the first electronic switch (M1) and the third electronic switch (M3) to a high resistance state, and to apply a voltage not equal to 0V to the non-inverting input terminal of the operational amplifier (O1), wherein if the voltage measured at the inverting input terminal of the operational amplifier (O1) is not equal to the voltage at the non-inverting input terminal of the operational amplifier (O1), the voltage-controlled voltage source is configured as a signal transmission type, otherwise the voltage-controlled current source is configured as a signal transmission type.

10. The output circuit (1) according to any one of claims 1 to 9, wherein: A current limiting resistor is arranged between the fifth electronic switch (M5) or the second diode (D2) and the first output terminal.

11. The output circuit (1) according to any one of claims 1 to 10, wherein: The fourth electronic switch (M4) is formed by means of two MOSFETs arranged in series and having opposite polarities with respect to the current carrying path, in order to ensure reverse polarity protection.

12. The output circuit (1) according to any one of claims 1 to 11, wherein: A third resistor (R3) is arranged in series with the first electronic switch (M1).

13. A method for operating an output circuit (1) according to one of claims 1 to 12, wherein: - when the signal transmission type of the voltage-controlled voltage source is to be adjusted, the first electronic switch, the third electronic switch (M3) and the possible fifth electronic switch (M5) are controlled to be turned on, and the possible second electronic switch and the possible fourth electronic switch (M2, M4) are controlled to be turned off; - when the signal transmission type of the voltage-controlled current source is to be adjusted, the first electronic switch and the third electronic switch are controlled to be turned off, and the possible second electronic switch (M2), the possible fourth electronic switch (M4) and the possible fifth electronic switch (M5) are controlled to be turned on, and - When the signal transmission type of the voltage-controlled current sink is to be adjusted: the first electronic switch (M1) is switched so that the first electronic switch is controlled by the voltage at the output end of the operational amplifier; the possible second electronic switch (M2) and the possible third electronic switch (M3) are controlled to be turned on; and the possible fourth electronic switch (M4) and the possible fifth electronic switch (M5) are controlled to be turned off.

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