ELECTRIC CIRCUITRY FOR SIGNAL TRANSMISSION

Abstract

An electric circuitry for signal transmission comprises a transmission gate having an input node to apply an input signal. The transmission gate includes a first transistor having an electric conductive channel of a first type of conductivity and a second transistor having an electric conductive channel of a second type of conductivity. The electric circuitry comprises a control circuit to control the signal transmission of the transmission gate. The control circuit is configured to generate a first and second control signal to control the conductivity of the first and second transistor in dependence on a voltage level of the input signal.

Claims

1. An electric circuitry for signal transmission, comprising: a transmission gate having an input node to apply an input signal and an output node to provide an output signal, a control circuit to control a signal transmission of the transmission gate between the input node and the output node, wherein the transmission gate includes a first transistor having an electric conductive channel of a first type of conductivity and a second transistor having an electric conductive channel of a second type of conductivity, wherein the first transistor has a control terminal to apply a first control signal to control the conductivity of the electric conductive channel of the first transistor, wherein the second transistor has a control terminal to apply a second control signal to control the conductivity of the electric conductive channel of the second transistor, wherein the control circuit is configured to generate the first and second control signal in dependence on a voltage level of the input signal to control the conductivity of the first and second transistor.

2. The electric circuitry of claim 1, comprising: an evaluation circuit to evaluate a level of the input signal, wherein the evaluation circuit is configured to evaluate whether the level of the input signal exceeds a first threshold value and a second threshold value.

3. The electric circuitry of claim 2, wherein the first threshold value corresponds to a threshold voltage of the first transistor and the second threshold value corresponds to the threshold voltage of the second transistor.

4. The electric circuitry of claim 1, wherein the first and second transistor are configured to be operated in a first and a second operation state, wherein a respective resistance of the conductive channel of the first and second transistor is higher in the first operation state than in the second operation state of the respective first and second transistor.

5. The electric circuitry of claim 4, wherein the control circuit is configured to change the operation state of the first transistor, when the evaluation circuit (300) detects that the level of the input signal crosses the first threshold value.

6. The electric circuitry of claim 5, wherein the control circuit is configured to generate the first control signal such that the first transistor is operated in the first operation state, when the evaluation circuit detects the level of the input signal above the first threshold value, wherein the control circuit is configured to generate the first control signal such that the first transistor is operated in the second operation state, when the evaluation circuit detects the level of the input signal below the first threshold value.

7. The electric circuitry of claim 4, wherein the control circuit is configured to change the operation state of the second transistor, when the evaluation circuit detects that the level of the input signal crosses the second threshold value.

8. The electric circuitry of claim 7, wherein the control circuit is configured to generate the second control signal such that the second transistor is operated in the first operation state, when the evaluation circuit detects the level of the input signal below the second threshold value, wherein the control circuit is configured to generate the second control signal such that the second transistor is operated in the second operation state, when the evaluation circuit detects the level of the input signal above the second threshold value.

9. The electric circuitry of claim 4, wherein the respective first operation state of the first and second transistor is a respective cutoff state of the first and second transistor, wherein the respective second operation state of the first and second transistor is a respective linear operation state of the first and second transistor.

10. The electric circuitry of claim 2, wherein the evaluation circuit comprises a first comparator being configured to compare the level of the input signal with the first threshold value and to provide a first comparator output signal indicating the level of the input signal being above or below the first threshold value, wherein the evaluation circuit comprises a second comparator being configured to compare the level of the input signal with the second threshold value and to provide a second comparator output signal indicating the level of the input signal being above or below the second threshold value.

11. The electric circuitry of claim 10, comprising: wherein the evaluation circuit comprises a first hold circuit to provide a first evaluation signal to the control circuit in response to the first comparator output signal, wherein the control circuit is configured to generate the first control signal in response to the first evaluation signal, wherein the evaluation circuit comprises a second hold circuit to provide a second evaluation signal to the control circuit in response to the second comparator output signal, wherein the control circuit is configured to generate the second control signal in response to the second evaluation signal.

12. The electric circuitry of claim 11, wherein the first hold circuit is configured to provide a holding function so that a state of the first control signal is kept unchanged, even if the evaluation circuit detects an instantaneous change of the value of the input signal swinging above and below the first threshold value, wherein the second hold circuit is configured to provide a holding function so that a state of the second control signal is kept unchanged even if the evaluation circuit detects an instantaneous change of the value of the input signal swinging above and below the second threshold value.

13. The electric circuitry of claim 1, wherein the electric conductive channel of the first transistor has a conductivity of an n-type, wherein the electric conductive channel of the second transistor has a conductivity of a p-type.

14. A communication system for cable data transmission, comprising: a first electric device to provide the data and a second electric device to receive the data, an electric circuitry for signal transmission according to claim 1, wherein the electric circuitry is connected between the first electric device and the second electric device, wherein the data is transmitted by the transmission gate of the electric circuitry from the first electric device to the second electric device.

15. The communication system of claim 14, wherein the first electric device is configured as a mobile phone or a computer or a microphone, wherein the second electric device is configured for signal processing the data received from the first electric device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 illustrates an embodiment of a transmission gate to transfer a signal between an input and output terminal of the transmission gate and the corresponding equivalent electric circuit of a transmission gate;

[0022] FIG. 2 shows a resistance characteristic of a transmission gate in dependence on an input voltage applied to the transmission gate;

[0023] FIG. 3 shows an electric circuit comprising a transmission gate connected between input and output resistors to form a variable potential divider;

[0024] FIG. 4 shows a distortion characteristic of a transfer function of a conventional transmission gate;

[0025] FIG. 5 shows an embodiment of an electric circuitry for signal transmission having an improved distortion characteristic of the transfer function of a transmission gate of the electric circuitry;

[0026] FIG. 6 illustrates a transfer function of a transmission gate having an improved distortion characteristic; and

[0027] FIG. 7 illustrates a communication system for cable data transmission.

DETAILED DESCRIPTION

[0028] FIG. 5 shows an embodiment of an electric circuitry 10 which allows to transfer an input signal V.sub.IN from one of the nodes A or B to the other one of the nodes A, B. For the following explanation, it is assumed that the input signal V.sub.IN is transmitted from node A being configured as an input node, to node B being configured as an output node. However, the reverse signal propagation path, i.e. the transmission from an input signal from node B to node A, is also possible by using the electric circuitry shown in FIG. 5.

[0029] The electric circuitry 10 comprises a transmission gate 100 having the input node A to apply the input signal V.sub.IN and the output node B to provide an output signal V.sub.OUT. The electric circuitry further comprises a control circuit 200 to control a signal transmission of the transmission gate 100 between the input node A and the output node B. The transmission gate 100 includes a first transistor 110 having an electric conductive channel of a first type of conductivity and a second transistor 12 (0 having an electric conductive channel of a second type of conductivity.

[0030] According to the exemplary embodiment of the electric circuitry 10 shown in FIG. 5, the electric conductive channel of the first transistor 110 may have a conductivity of an n-type. In particular, the first transistor 110 may be configured as an n-channel MOSFET. The electric conductive channel of the second transistor 120 may have a conductivity of a p-type. In particular, the second transistor 120 may be connecting component as a p-channel MOSFET.

[0031] The first transistor 110 has a control terminal C110 to apply a first control signal CS1 to control the conductivity of the electric conductive channel of the first transistor 110. The second transistor 120 has a control terminal C120 to apply a second control signal CS2 to control the conductivity of the electric conductive channel of the second transistor 120. The control circuit 200 is configured to generate the first and second control signals CS1 and CS2 in dependence on a voltage level of the input signal V.sub.IN to control the conductivity of the first and second transistors 110 and 120.

[0032] The electric circuitry 10 comprises an evaluation circuit 300 to evaluate a level of the input signal V.sub.IN. The evaluation circuit 300 is configured to evaluate whether the level of the input signal V.sub.IN exceeds a first threshold value V.sub.THN and a second threshold value V.sub.THP. The first threshold value V.sub.THN corresponds to a threshold voltage of the first transistor 110, and the second threshold value V.sub.THP corresponds to the threshold voltage of the second transistor 120.

[0033] The threshold voltage of a transistor is the voltage between the control/gate terminal and the input/source terminal of the transistor from which a significant current flows through the conductive channel of the transistor, i.e. a significant current flow occurs when the input voltage applied between the input/source terminal and the control/gate terminal exceeds the threshold voltage of the transistor.

[0034] The first and second transistor 110 and 120 are configured to be operated in a first and a second operation state. A respective resistance of the conductive channel of the first and second transistor 110, 120 is higher in the first operation state than in the second operation state of the respective first and second transistor. The first operation state specifies the so-called “non-conductive” state of the transistor. The second operation state specifies the so-called “conductive” state of the transistor.

[0035] The control circuit 200 is configured to change the operation state of the first transistor 110, for example a NMOS transistor, when the evaluation circuit 300 detects that the level of the input signal V.sub.IN crosses the first threshold value V.sub.THN. The control circuit 200 is configured to generate the first control signal CS1 such that the first transistor 110 is operated in the first operation state (“non-conductive state”), when the evaluation circuit 300 detects the level of the input signal V.sub.IN above the first threshold value V.sub.THN. The control circuit 200 is further configured to generate the first control signal CS1 such that the first transistor 110 is operated in the second operation state (“conductive state”), when the evaluation circuit 200 detects the level of the input signal V.sub.IN below the first threshold value V.sub.THN. The control circuit 200 is configured to change the operation state of the second transistor 120, for example a PMOS transistor, when the evaluation circuit 300 detects that the level of the input signal V.sub.IN crosses the second threshold value V.sub.THP. In particular, the control circuit 200 is configured to generate the second control signal CS2 such that the second transistor 120 is operated in the first operation state (“non-conductive state”), when the evaluation circuit 300 detects the level of the input signal V.sub.IN below the second threshold value V.sub.THP. The control circuit 200 is further configured to generate the second control signal CS2 such that the second transistor 120 is operated in the second operation state (“conductive state”), when the evaluation circuit 300 detects the level of the input signal V.sub.IN above the second threshold value V.sub.THP.

[0036] The respective first operation state of the first and second transistor 110 and 120 is the respective cut-off state of the first and second transistor. The respective second operation state of the first and second transistor 110 and 120 is a respective linear operation state of the first and second transistor, i.e. the resistance of the electric channel of the transistor shows a linear resistance characteristic.

[0037] As shown in the embodiment of the electric circuitry of FIG. 5, the evaluation circuit 300 comprises a first comparator 310 being configured to compare the level of the input signal V.sub.IN with the first threshold value V.sub.THN, and to provide a first comparator output signal S310 indicating the level of the input signal V.sub.IN being above or below the first threshold value V.sub.THN. The evaluation circuit 300 further comprises a second comparator 320 being configured to compare the level of the input signal V.sub.IN with the second threshold value V.sub.THP, and to provide a second comparator output signal S320 indicating the level of the input signal V.sub.IN being above or below the second threshold value V.sub.THP.

[0038] The evaluation circuit 300 comprises a first hold circuit 330 to provide a first evaluation signal S330 to the control circuit 200 in response to the first comparator output signal S310. The evaluation circuit 300 further comprises a second hold circuit 340 to provide a second evaluation signal S340 to the control circuit 200 in response to the second comparator output signal S320.

[0039] The first hold circuit 330 is configured to provide a holding function so that a state of the first control signal CS1 is kept unchanged even if the evaluation circuit 300 detects an instantaneous change of the value of the input signal V.sub.IN swinging above and below the first threshold value V.sub.THN. In the same way, the second hold circuit 340 is configured to provide a holding function so that a state of the second control signal CS2 is kept unchanged even if the evaluation circuit 300 detects an instantaneous change of the value of the input signal V.sub.IN swinging above and below the second threshold value V.sub.THP.

[0040] The control circuit 200 is configured to generate the first control signal CS1 in response to the first evaluation signal S330. As shown in FIG. 5, the control circuit 200 may comprise a logic gate 210 being coupled to a control input terminal C200 to apply an external control signal CS. The external control signal CS serves to operate the transmission gate 100 in a conductive or non-conductive operation mode. The first evaluation signal S330 is applied to the input side of the logic gate 210. As shown in the exemplary embodiment of the electric circuitry 10 of FIG. 5, the first evaluation signal S330 can be applied to the input side of the logic gate 210 via an inverter 230. The output side of the logic gate 210 is connected to the control terminal C110 of the first transistor 110 of the transmission gate 100.

[0041] The control circuit 200 further comprises a logic gate 220 being coupled with its output side to the control terminal C120 of the second transistor 120 of the transmission gate 100. An input side of the logic gate 220 is connected to the external control terminal C200 of the control circuit to apply the external control signal CS. The input side of the logic gate 220 is further coupled to the output of the second hold circuit 340 to apply the second evaluation signal S340 to the input side of the logic gate 220. According to the exemplary embodiment of the electric circuitry 10 shown in FIG. 5, the second evaluation signal S340 can be applied to the input side of the logic gate 220 via an inverter 240. When the evaluation circuit 300 detects by the second comparator 320 that the input signal V.sub.IN falls below the second threshold value V.sub.THP, the control circuit 200 generates the second control signal CS2 such that the second transistor 120 is operated in the first operation state (“non-conductive state”). The first transistor 110 is operated in the second operation state (“conductive state”), as long as the input signal V.sub.IN is below the first threshold value V.sub.THN. In this case, the conductive state of the transmission gate 100 is just provided by the first transistor 110.

[0042] When the evaluation circuit detects, by the first comparator circuit 310, that the input signal V.sub.IN exceeds the first threshold value V.sub.THN, the control circuit 200 generates the first control signal CS1 to operate the first transistor 110 in the first operation state (“non-conductive state”). The second transistor 120 is operated in the second operation state (“conductive state”), as long as the input signal V.sub.IN is above the second threshold value V.sub.THP. In this case the transmission gate 100 conducts only by means of the second transistor 120.

[0043] When the evaluation circuit 300 detects by the first and second comparators 310, 330 that the input voltage V.sub.IN is between the first threshold value V.sub.THN and the second threshold value V.sub.THP, both of the first and second transistors 110, 120 of the transmission gate 100 are operated in the second operation state (“conductive state”). The configuration of the electric circuitry shown in FIG. 5 enables to prevent a signal swing of the input signal V.sub.IN toggling one of the transmission gate transistors 110 and 120 between cut-off and linear operation. FIG. 6 shows the distortion characteristic of the transfer function of the transmission gate 110 of the electric circuitry 10, as shown in FIG. 5. As illustrated in FIG. 6, the peaks of the distortion characteristics shown in FIG. 4 are flattened and thus nearly removed. The area of a transmission gate needed to achieve a specific maximum distortion specification can be reduced. The amount of reduction of the total harmonic distortion THD shown in FIG. 6 is dependent on the specific distortion specification, signal and power supply voltages and CMOS technology used.

[0044] FIG. 7 illustrates a communication system for cable data transmission. The communication system comprises a first electric device 1 to provide the data and a second electric device 2 to receive the data. The first electric device 1 may be configured, for example, as a mobile phone or a computer or a microphone. The second electric device 2 may be configured for signal processing the data received from the first electric device 1. The second electric device 2 may be configured, for example, as an analog-to-digital converter, a recording device, a headset or a sensor device.

[0045] The electric circuitry 10 is connected between the first electric device 1 and the second electric device 2. The data is transmitted by the transmission gate 100 of the electric circuitry 10 from the first electric device 1 to the second electric device 2. The electric circuitry 10 can be advantageously used to transmit data between the first electric device 1 and the second electric device 2 with low signal distortion, especially, when the transmission gate is loaded by a finite impedance so that a voltage divider is formed between the transmission gate 100 and an input resistance of the second electric device 2.