DE102023104733B3 - Analog driver circuit for piezo components and control unit - Google Patents

Abstract

In one embodiment, the analog driver circuit (1) comprises an amplification part (2) with:- a supply voltage input (VDD), a signal voltage input (DAC), a base voltage input (-VDD, GND) and a signal output (VCP),- a first (T1) and a second transistor (T2) which are connected to the supply voltage input (VDD),- a third transistor (T3) which is connected to the first transistor (T1) and whose base is connected to the signal voltage input (DAC),- a fourth transistor (T4) which is connected to the second transistor (T2), the fourth transistor (T4) leading to the signal output (VCP), and- a fifth (T5) and a sixth transistor (T6) which are connected to the base voltage input (-VDD, GND) and whose bases are connected to the supply voltage input (VDD), the sixth transistor (T6) being connected to the third transistor (T3) and to the fourth transistor (T4) and the fifth transistor (T5) is connected to the supply voltage input (VDD) via a current limiting resistor (R6).

Description

An analog driver circuit for piezo components is specified. In addition, a control unit with such a driver circuit is specified.

The printed publications EN 10 2005 034 162 A1 , EN 10 2008 034 324 B4 , DE 20 2014 104 676 U1 , EN 10 2009 041 937 A1 , EN 10 2013 103 754 B3 , EN 10 2017 122 881 A1 and EN 10 2017 106 188 B3 are aimed at driver circuits.

The printed publications US 7 271 520 B2 , US 5 982 304 A , US 2002/0 084 721 A1 , US 2006/0 028 095 A1 , US 2009/0 146 533 A1 , US 2012/0 013 220 A1 , EP 2 600 224 A1 , US 8 605 053 B2 , EP 2 763 317 A2 , US 8 854 319 B1 , EP 3 018 824 A1 , EP 3 065 029 A1 , EP 2 472 365 B1 and US 4 994 955 A concern driver circuits.

In the printed publications US 2019/0 067 552 A1 , US 2019/0 334 077 A1 and US 2021/0 141 456 A1 Piezo-haptic actuators are described.

One task to be solved is to provide a driver circuit that is reliable and can be constructed efficiently.

This object is achieved, inter alia, by a driver circuit and by a control unit with the features of the independent patent claim. Preferred developments are the subject of the dependent claims.

The analog driver circuit described here is intended, for example, for piezo components, in particular for generating a haptic feedback effect.

• - einen Versorgungspannungseingang, einen analogen Signalspannungseingang, einen Grundspannungseingang und einen analogen Signalausgang,
• - einen ersten Transistor und einen zweiten Transistor, die an den Versorgungspannungseingang angeschlossen sind und deren Basen miteinander verbunden sind,
• - einen dritten Transistor, der an den ersten Transistor angeschlossen ist und dessen Basis mit dem Signalspannungseingang verbunden ist,
• - einen vierten Transistor, der an den zweiten Transistor angeschlossen ist und dessen Basis mit einem Rückkopplungskanal verbunden ist, wobei der vierte Transistor zum Signalausgang führt, und
• - einen fünften Transistor und einen sechsten Transistor, die an den Grundspannungseingang angeschlossen sind und deren Basen mit dem Versorgungspannungseingang verbunden sind, wobei der sechste Transistor ferner an den dritten Transistor und an den vierten Transistor angeschlossen ist und der fünfte Transistor ferner über einen Strombegrenzungswiderstand an den Versorgungspannungseingang angeschlossen ist. Der Strombegrenzungswiderstand kann unmittelbar zwischen dem Versorgungspannungseingang und einem Emitter oder einem Kollektor des fünften Transistors liegen.

The analog driver circuit comprises an amplification part, the amplification part comprising:

• - a supply voltage input, an analog signal voltage input, a base voltage input and an analog signal output,
• - a first transistor and a second transistor connected to the supply voltage input and having their bases connected to each other,
• - a third transistor connected to the first transistor and having its base connected to the signal voltage input,
• - a fourth transistor connected to the second transistor and having a base connected to a feedback channel, the fourth transistor leading to the signal output, and
• - a fifth transistor and a sixth transistor which are connected to the base voltage input and whose bases are connected to the supply voltage input, the sixth transistor being further connected to the third transistor and to the fourth transistor and the fifth transistor being further connected to the supply voltage input via a current limiting resistor. The current limiting resistor can be located directly between the supply voltage input and an emitter or a collector of the fifth transistor.

The transistors are in particular bipolar transistors and not metal-oxide-semiconductor field-effect transistors, also known as MOSFETs.

Since the supply voltage input and a supply voltage line within the driver circuit are at the same electrical potential, no distinction is made between these components below and we refer uniformly to the supply voltage input. The same applies to the signal voltage input, the base voltage input, the signal output and the feedback channel.

The term "connected" refers in particular to an emitter or collector of the transistor in question. This means, for example, that if a transistor is "connected" to another component, this means an indirect or direct electrical connection between this component and the emitter or collector of the transistor in question, unless otherwise indicated.

The feedback channel, for example, refers to inverting and/or non-inverting feedback.

A voltage at the supply voltage input is higher than a voltage at the base voltage input. For example, if a voltage of +VDD is present at the supply voltage input, the voltage at the base voltage input is between -VDD and GND, or the base voltage input is then -W or GND. GND refers to a ground connection, i.e. specifically 0 V.

Piezo-haptic feedback is playing an increasing role in human-machine interaction and can be used, for example, in industrial devices, household appliances or display devices in the automotive sector. Information, such as about a system's behavior, is transmitted to a user via a short haptic impulse, such as a vibration.

To penetrate the market with haptic applications, electronic circuitry that is cost-effective, market-oriented, energy-efficient, environmentally-friendly and production-friendly is required.

One method for this is to build a driver circuit from discrete electronic components. Such components are more readily available on the market than various components based on application-specific integrated circuits, also known as application-specific integrated circuits or ASICs for short. The driver circuit described here is an analog circuit made of discrete components.

Comparable circuits, on the other hand, are usually based on special components for controlling piezohaptic applications and are poorly available on the market, are often significantly more expensive and are sometimes not qualified for applications in the automotive sector.

An alternative method for operating piezo components is a so-called H-bridge configuration, which is described in the publication US 7 271 520 B2 This method describes only H-Bridge configurations and is supplied with a PWM signal and buffer and is designed for positive voltage only.

The driver circuit described here, however, also enables operation with bipolar control voltage, so that the piezomechanical performance of the system can be improved. This means that not only the expansion of the piezo under positive voltage is used, but also the contraction under negative voltage, so that the total deflection is significantly increased.

Furthermore, the publication US 7 271 520 B2 The embodiment shown has the disadvantage that the single-stage H-bridge configuration either only allows piezo components with a relatively low capacitance to be operated or the transistors used have to be designed as power transistors, which leads to increased costs and increased space requirements.

In the print US 5 982 304 A A solution with two driver ICs connected in series is described. The design proposed here does not require the use of special driver ICs and is therefore more cost-effective. IC stands for integrated circuit.

In the print US 2002/0 084 721 A1 An alternative embodiment is presented which differs significantly from the push-pull configuration described here.

In the print US 2006/0 028 095 A1 A signal is amplified using an operational amplifier IC and a comparator IC. No operational amplifier ICs or comparator ICs are used in the driver circuit described here.

In the print US 2009/0 146 533 A1 Two OP-AMP ICs are used to transmit a signal to both contacts of a piezo. The embodiment shown is also limited to a control voltage of +40 V. The driver circuit described here, on the other hand, does not use OP-AMP ICs and does not have the restriction regarding the signal level.

In the print US 2012/0 013 220 A1 A design is presented in which PWM signals are converted into analog signals. A series of OP-AMPs are used for this purpose. In the described However, the driver circuit used uses analog input signals and not PWM signals, especially between 0 V and 3.3 V, and the use of OP-AMPs is avoided. Furthermore, concepts based on PWM signals are susceptible to overtones, which can lead to noise in the piezo components. PWM stands for pulse width modulation.

In the print EP 2 600 224 A1 A technical embodiment for sensing in a haptic feedback application is described. The driver circuit described here, however, does not concern a sensing function, but rather only the generation of the control signal for the deflection of the piezo component.

The publication US 8 605 053 B2 describes a driver circuit in the form of a full-bridge configuration to provide the drive signal for the haptic feedback to the piezo component. The driver circuit described here differs in that a half-bridge configuration and/or a push-pull configuration is used.

In the print EP 2 763 317 A2 A system configuration is discussed, but this document does not provide any information on the design of an amplifier circuit or the wiring of a piezohaptic component with a control signal.

The publication US 8 854 319 B1 suggests a boost converter with a transformer. The driver circuit described here, however, does not require a transformer.

The printed publications EP 3 018 824 A1 , EP 3 065 029 A1 and EP 2 472 365 B1 refer to piezo sensors. The circuit described here serves as a driver solution.

In the print US 4 994 955 A A solution is discussed in which a special driver IC uses several MOSFETs and inductors. The driver circuit described here does not use a driver IC, MOSFETs or inductors.

The driver circuit described here comprises or consists of two parts, for example. There can be an amplifier part on the one hand and a half-bridge circuit for transmitting a signal to the piezo component on the other. The signal level of the signal is, for example, around 120 V.

The preferred active components are exclusively automotive-certified npn transistors and pnp transistors.

The first part of the circuit, the amplifier part, ensures in particular that the input signal is sufficiently amplified. For this purpose, a series of npn transistors and pnp transistors are coupled together in such a way that the scattering of the electrical properties of the active components has no significant influence on the signal to be generated. This means that many transistors available on the market can be used and the selection of inexpensive components is made much easier. Furthermore, the space required on a circuit board is comparable to solutions based on ASIC elements. The latter, however, are significantly more expensive than the discrete components used in the solution presented.

In addition, the proposed solution provides a significantly better signal quality than known solutions using ASIC. When using ASIC components, overtones are usually present in the signal. These lead to additional and unwanted noise at the piezo component, which is extremely disadvantageous for haptic feedback applications.

The second part of the driver circuit, which can be configured as a switch, uses a push-pull half-bridge configuration, for example. The npn transistors and the pnp transistors of the push-pull configuration are regulated via an ohmic voltage divider. The highest achievable voltage can be set via a second ohmic voltage divider, as this acts as feedback for the amplifier part of the circuit.

The driver circuit described here therefore does not require any transformers, MOSFETs or driver ICs. In addition, the signal quality of the proposed solution is significantly better and the costs are lower than those of the state-of-the-art solutions.

According to at least one embodiment, the driver circuit further comprises a further circuit part. The further circuit part is preferably connected downstream of the amplification part.

According to at least one embodiment, the further circuit part comprises a seventh transistor, the base of which is connected to the second transistor and/or to the fourth transistor. For example, the seventh transistor is connected to the supply voltage input.

According to at least one embodiment, the further circuit part comprises an eighth transistor, the base of which is connected to the second transistor and/or to the fourth transistor. For example, the eighth transistor is connected to the base voltage input,

According to at least one embodiment, the seventh transistor and the eighth transistor are connected to the signal output. One or more resistors can be located between the seventh and eighth transistors and the signal output.

According to at least one embodiment, the bases of the seventh transistor and the eighth transistor are connected to the fourth transistor via an electrical resistor. This means, for example, that only this associated electrical resistor is interposed between the relevant collector or emitter of the fourth transistor and the bases of the seventh and eighth transistors.

According to at least one embodiment, the seventh transistor is an npn transistor and/or the eighth transistor is a pnp transistor.

According to at least one embodiment, the driver circuit further comprises one or more circuit extensions. The at least one circuit extension is constructed like the further circuit part. This means, for example, that the at least one circuit extension and the further circuit part have the same circuit structure, in particular the same number and connection of transistors and resistors. It is possible that the at least one circuit extension and the further circuit part differ from one another in the types of transistors and/or electrical resistors used. If several of the circuit extensions are present, all circuit extensions can be of the same construction or circuit extensions with different structures can be combined with one another.

According to at least one embodiment, the at least one circuit extension and the further circuit part are each connected to the fourth transistor and to the signal output. It is possible for the at least one circuit extension and the further circuit part to have the same electrical connection points to the amplification part and/or to the signal output.

According to at least one embodiment, the feedback channel is connected to the signal output and to a ground connection and/or the base voltage input via an electrical resistor. The feedback channel can comprise an electrical line that runs electrically from between these two resistors directly to the base of the fourth transistor.

According to at least one embodiment, the first transistor and/or the second transistor are connected to the supply voltage input via a further electrical resistor. These resistors can be the same size or different from one another.

According to at least one embodiment, the fifth transistor and the sixth transistor are connected directly to the base voltage input. Alternatively, an electrical resistor can be connected between them.

According to at least one embodiment, the bases of the first transistor and/or the second transistor are connected to an emitter or a collector of the third transistor via an additional electrical resistor. It is possible that this resistor has a higher resistance than the resistors between the first and second transistors and the supply voltage input.

According to at least one embodiment, the amplification part and/or the further circuit part and/or the at least one circuit extension or the entire driver circuit is free of one, some or all of the following components: transformer, field effect transistor, inductance, digital integrated circuits, such as an ASIC. This means that at least one part of the driver circuit can consist of the bipolar transistors and electrical resistors.

According to at least one embodiment, the first transistor and/or the second transistor are a pnp transistor. Alternatively or additionally, the third transistor, the fourth transistor, the fifth transistor and/or the sixth transistor are an npn transistor.

According to at least one embodiment, the supply voltage input is configured for a voltage between 40 V and 250 V inclusive. For example, this voltage is at least 80 V or at least 100 V and/or this voltage is at most 200 V or at most 140 V.

According to at least one embodiment, the signal voltage input is set up for at least one voltage between -10 V and 10 V inclusive. For example, a voltage at the signal voltage input is intended to vary between 0 V and 3.3 V inclusive or between 0 V and 5 V inclusive or between -5 V and +5 V inclusive or between -3 V and +3 V inclusive in order to control the piezo at the signal output.

According to at least one embodiment, the signal output is set up for a capacitance, in particular of the piezo and for example against a ground connection, between 0.1 µF and 0.1 mF inclusive. For example, this value is at least 0.5 µF and/or at most 10 µF or at most 5 µF.

In addition, a control unit is specified. The control unit comprises one or more driver circuits, as described in connection with one or more of the above-mentioned embodiments. Features of the driver circuit are therefore also disclosed for the control unit and vice versa.

• - eine Digital-zu-analog-Steuerschaltung,
• - eine der Digital-zu-analog-Steuerschaltung direkt oder indirekt nachgeschaltete Puffer-Schaltung (12), zum Beispiel zur Impedanzanpassung und/oder zur Vorverstärkung,
• - eine der Puffer-Schaltung direkt oder indirekt nachgeschaltete Treiberschaltung, und
• - einen oder mehrere der Treiberschaltung direkt oder indirekt nachgeschaltete Piezo-haptischen Aktuatoren.

The control unit includes:

• - a digital-to-analog control circuit,
• - a buffer circuit (12) connected directly or indirectly downstream of the digital-to-analogue control circuit, for example for impedance matching and/or pre-amplification,
• - a driver circuit connected directly or indirectly downstream of the buffer circuit, and
• - one or more piezo-haptic actuators connected directly or indirectly downstream of the driver circuit.

A driver circuit and a control unit described here are explained in more detail below with reference to the drawing using exemplary embodiments. The same reference symbols indicate the same elements in the individual figures. However, no scale references are shown; rather, individual elements may be shown exaggeratedly large for better understanding.

• 1 ein schematisches Blockdiagramm eines Ausführungsbeispiels einer Ansteuerungseinheit mit einer hier beschriebenen Treiberschaltung, und
• 2 und 3 schematische Schaltbilder von Ausführungsbeispielen von hier beschriebenen Treiberschaltungen.

Show it:

• 1 a schematic block diagram of an embodiment of a control unit with a driver circuit described here, and
• 2 and 3 schematic circuit diagrams of embodiments of driver circuits described here.

In 1 an example of a control unit 10 is shown. The control unit 10 comprises a digital-to-analog control circuit 11, a buffer circuit 12 connected downstream of this for impedance matching and/or pre-amplification, a driver circuit 1 connected downstream of this and at least one piezohaptic actuator 14 connected downstream of this.

In one possible embodiment, an analog signal, for example with a voltage between 0 V and 3.3 V or between 0 V and 5 V, is made available via a DAC output of the digital-to-analog control circuit 11. The digital-to-analog control circuit 11 is, for example, a pController, such as an MCU DAC, or a function generator. The digital-to-analog control circuit 11 thus provides an input signal for the driver circuit 1.

This signal from the digital-to-analog control circuit 11 can optionally be pre-amplified via the buffer circuit 12, for example an MCP6421T or a TLV379IDBVT, for example from 0..3V to 0..5V. Additionally or alternatively, the buffer circuit 12 can serve to impedance match this signal. The buffer circuit 12 can also be omitted, so that the driver circuit 1 can receive the input signal directly from the digital-to-analog control circuit 11.

In the driver circuit 1, the signal is then amplified and forwarded to the piezohaptic component 14, for example via an H-bridge circuit.

With such a control unit 10, in which the driver circuit 1 is integrated, haptic feedback can be implemented on, for example, screens, switching elements and/or handles to improve the user experience. Furthermore, a sensor circuit can be integrated into the overall system 10 (not shown), so that the actuation of, for example, a switching element triggers a signal from the piezohaptic component 14, whereby this signal can be recognized and evaluated by the control system.

In 2 an example of the driver circuit 1 is shown schematically. The driver circuit 1 comprises a supply voltage input VDD, for example 120 V, an analog signal voltage input DAC, for example 0 to 5 V, a base voltage input, which is for example at -VDD or at GND, and an analog signal output VCP. The signal output VCP leads to the piezohaptic component 14, which is not part of the driver circuit 1 and which is symbolized as capacitance Cp.

A first amplification part 2 of the driver circuit 1 comprises several bipolar transistors T1..T6, which are designed as pnp transistors or npn transistors, see the circuit symbols in 1 . There are also several electrical resistors R3..R7. The emitters of the transistors T1, T2 are connected to the supply voltage input VDD via the resistors R3, R4, the emitters of the transistors T5, T6 are connected directly to the base voltage input -VDD. Furthermore, the bases of the transistors T5, T6 are connected to the supply voltage input VDD via a current limiting resistor R6, as is the collector of the transistor T5. The current limiting resistor R6 limits the maximum current through the circuit. The maximum current is, for example, a maximum of 2 A or a maximum of 1 A.

The base of the transistor T3 is directly connected to the signal voltage input DAC. The emitter of the transistor T3 is connected to the collector of the transistor T6 and also connected to the emitter of the transistor T6. The collectors of the transistors T3, T4 are connected to the collectors of the transistors T1, T2. Furthermore, the collector of the transistor T3 is connected to the bases of the transistors T1, T2 via a resistor R5.

The base of the transistor T4 is connected to a feedback channel F. The feedback channel F branches off between two resistors R1, R2, which are connected in series in parallel to the capacitance Cp and run to GND.

The driver circuit 1 also includes a further circuit part 3, which forms an additional amplifier stage after the first amplification part 2. The circuit part 3 includes the transistors T7, T8, whose bases are connected to the collectors of the transistors T2, T4 via a resistor R7. The collectors of the transistors T7, T8 are connected directly to the supply voltage input VDD or to the base voltage input -VDD. The emitters of the transistors T7, T8 are connected to one another via the resistors R8, R9 connected in series. The signal output VCP is tapped between the resistors R8, R9 via the downstream resistor R10 to the capacitance Cp.

The driver circuit 1 is thus, as described above, supplied with the analog input signal DAC and the supply voltage +VDD, for example 120 V, as well as the base voltage -VDD.

As in 2 The amplifier section 2 is shown, comprising the transistors T1..T6, differentially coupled between DAC and GND. The transistors T3 and T4 are non-inverting and inverting amplifier sections. The load transistors T1 and T2 form an active current mirror and enable the conversion of the small differential input signal between DAC and GND to a so-called single-ended amplified output signal VCP.

Transistors T5 and T6 are controlled by the supply voltage +VDD and -VDD to sink them to a certain amount of current based on their respective base-emitter voltage. Transistors T7 and T8 form a second stage of amplification in the output. The output of transistor T4 is amplified by transistor T7, this configuration is also called common emitter configuration.

The transistors T7 and T8 are stabilized via the two resistors R8 and R9, thus ensuring the stability of the output signal VCP. The piezohaptic load Cp is supplied with the output signal VCP via the resistor R10. The resistors R1 and R2 feed a feedback signal back to the inverting part of the amplifier 2 so that the amplifier 2 is coupled in the so-called follower configuration.

The piezo-haptic actuator 14 is constructed, for example, as described in the publications US 2019/0 067 552 A1 , US 2019/0 334 077 A1 or US 2021/0 141 456 A1 The disclosure content of these publications with regard to the piezo-haptic actuator 14 is incorporated by reference.

In all other respects, the statements on 1 in the same way for 2 , and vice versa.

In the 2 The driver circuit 1 shown as an example can be extended as shown in 3 This is particularly useful when a larger haptic load Cp is to be put into operation.

Thus, several or only one circuit extensions 4 are available. The circuit extensions 4, according to 3 If three of the circuit extensions 4 are present, they are all connected to a first tapping point A and a second tapping point B, together with the additional circuit part 3. The additional circuit part 3 and the circuit extensions 4 can have the same structure. In other words, the additional circuit part 3 can be present four times if the transistors T7, T8 and T9, T10 as well as the resistors R8, R9 and R11, R12 are the same.

With the components listed in the following table and the 2 and 3 As an embodiment, for example, a piezoelectric load Cp of 1 µF ≤ Cp ≤ 3.6 µF, in particular Cp = 3.6 µF, can be supplied with the circuits shown: Component Designation Type R1 511 kΩ Resistance R2 13.3kΩ Resistance R3, R4 511Ω Resistance R5 2.5kΩ Resistance R6 100kΩ Resistance R7 10kΩ Resistance R8, R11 147Ω Resistance R9, R12 46.4Ω Resistance T1, T2, T8, T10 FMMT555 pnp transistor T3, T4, T5, T6, T7, T9 FCX495 npn transistor Cp 6005H090V120 TDK PowerHap 6005 +VDD 120V Tension

The value of the resistor R6 essentially determines the current strength, so the current strength can be adjusted via the resistor R6.

For example, the values of the resistors R1..R5 and R7..R11 may deviate from the values given in the table by up to 30% or up to 10% or up to 3%.

It is possible that the ratios shown in the table above are derived from the resistance values for R1/R2 and/or for R8/R9 and/or for R11/R12 individually or in combination with a tolerance of not more than 30% or not more than 10% or not more than 3% in examples of driver circuit 1.

In all other respects, the statements on the 1 and 2 in the same way for 3 , and vice versa.

The components shown in the figures preferably follow one another in the order given, in particular directly one after the other, unless otherwise described. Components that do not touch one another in the figures preferably have a distance from one another. If lines are drawn parallel to one another, the associated surfaces are preferably also aligned parallel to one another. In addition, the relative positions of the drawn components to one another are correctly reproduced in the figures, unless otherwise stated.

List of reference symbols

1

Driver circuit

2

Reinforcement part

3

further circuit part

4

Circuit extension

10

Control unit

11

Digital-to-analog control circuit

12

Buffer circuit

14

Piezo-haptic actuator

A

first tap point

B

second tap point

Cp

Piezo capacitance

F

Feedback channel, feedback channel

T

Bipolar transistor

R

electrical resistance

GND

Earth connection, ground voltage input

VAC

analog signal voltage input

VCP

analog signal output

VDD

Supply voltage input

Claims (10)

Analog driver circuit (1) with an amplification part (2), the amplification part (2) comprising: - a supply voltage input (VDD), an analog signal voltage input (DAC), a base voltage input (-VDD, GND) and an analog signal output (VCP), - a first transistor (T1) and a second transistor (T2) which are connected to the supply voltage input (VDD) and whose bases are connected to one another, - a third transistor (T3) which is connected to the first transistor (T1) and whose base is connected to the signal voltage input (DAC), - a fourth transistor (T4) which is connected to the second transistor (T2) and whose base is connected to a feedback channel (F), the fourth transistor (T4) leading to the signal output (VCP), and - a fifth transistor (T5) and a sixth transistor (T6) which are connected to the base voltage input (-VDD, GND) and whose bases are connected to the supply voltage input (VDD), wherein the sixth transistor (T6) is further connected to the third transistor (T3) and to the fourth transistor (T4), and the fifth transistor (T5) is further connected to the supply voltage input (VDD) via a current limiting resistor (R6). Driver circuit (1) according to the preceding claim, further comprising a further circuit part (3) which is connected downstream of the amplification part (2), with - a seventh transistor (T7), the base of which is connected to the second transistor (T2) and to the fourth transistor (T4) and which is connected to the supply voltage input (VDD), and - an eighth transistor (T8), the base of which is also connected to the second transistor (T2) and to the fourth transistor (T4) and which is connected to the base voltage input (-VDD, GND), the seventh transistor (T7) and the eighth transistor (T8) being connected to the signal output (VCP). Driver circuit (1) according to the preceding claim, in which the bases of the seventh transistor (T7) and the eighth transistor (T8) are connected to the fourth transistor (T4) via an electrical resistor (R7), wherein the seventh transistor (T7) is an npn transistor and the eighth transistor (T8) is a pnp transistor. Driver circuit (1) according to one of the two preceding claims, further comprising at least one circuit extension (4), wherein the circuit extension (4) is constructed like the further circuit part (3), so that the at least one circuit extension (4) and the further circuit part (3) are each connected to the fourth transistor (T4) and to the signal output (VCP). Driver circuit (1) according to one of the preceding claims, in which the feedback channel (R) is connected to the signal output (VCP) and to a ground connection (GND) via an electrical resistor (R1, R2). Driver circuit (1) according to one of the preceding claims, in which the first transistor (T1) and the second transistor (T2) are each connected to the supply voltage input (VDD) via a further electrical resistor (R3, R4), wherein the fifth transistor (T5) and the sixth transistor (T6) are connected directly to the base voltage input (-VDD, GND). Driver circuit (1) according to one of the preceding claims, in which the bases of the first transistor (T1) and the second transistor (T2) are connected to the third transistor (T3) via an additional electrical resistor (R5). Driver circuit (1) according to one of the preceding claims, wherein at least the amplification part (2) is free of transformers, field effect transistors, inductors and digital integrated circuits. Driver circuit (1) according to one of the preceding claims, in which the first transistor (T1) and the second transistor (T2) are each a pnp transistor and the third transistor (T3), the fourth transistor (T4), the fifth transistor (T5) and the sixth transistor (T6) are each an npn transistor, wherein the supply voltage input (VDD) is set up for a voltage between 40 V and 250 V inclusive and the signal voltage input (DAC) is set up for at least one voltage between -10 V and 10 V inclusive, where the signal output (VCP) is set up for a capacitance (Cp) against a ground connection (GND) between 0.1 µF and 0.1 mF inclusive. Control unit (10) with - a digital-to-analog control circuit (11), - a buffer circuit (12) connected downstream of the digital-to-analog control circuit (11) for impedance matching and/or pre-amplification, - a driver circuit (1) according to one of the preceding claims connected downstream of the buffer circuit (12), and - a piezohaptic actuator (14) connected downstream of the driver circuit (1).

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