A line driver which is especially suitable for wirebound data transmission at high bit rates, comprising several parallel-connected driver stages ( 3 ) respectively comprising a first pair of transistors consisting of two transistors ( 4, 5 ) which are controlled in a differential manner according to digital data to be transmitted, and a second pair of transistors ( 4, 5 ). The transistors belonging to the second pair of transistors ( 6, 7 ) are series-connected to a corresponding transistor ( 4, 5 ) of the first pair of transistors. The individual driver stages ( 3 ) are connected by the transistors ( 6, 7 ) of the second pair of transistors in a parallel manner to both the terminals of the line driver. Each driver stage ( 3 ) is associated with a control circuit ( 2 ) with transfer gates ( 14, 15 ), producing the differential control signals (VG A , VG B ) for the two transistors ( 4, 5 ) of the corresponding first pair of transistors.
1. A line driver for data transmission comprising:
a plurality of driver stages, each driver stage comprising:
a first transistor pair with first and second transistors which are differentially actuated as a function of the data which is to be transmitted; and
a second transistor pair with a first and second cascade transistor,
the first cascade transistor of the second transistor pair connected in series between the first transistor of the first transistor pair of the same driver stage and a first output of the line driver, and the second cascade transistor connected in series between the second transistor of the first transistor pair of the same driver stage and a second output of the line driver, in such a way that the individual driver stages are connected in each case in parallel via the corresponding second transistor pair to the first and second outputs of the line driver; and
a control circuit allocated to each driver stage for creating differential control signals (VG A , VG B ) to actuate the two transistors of the first transistor pair of the individual driver stage, whereby each control circuit is designed in such a way that, when the differential control signals (VG A , VG B ) are created, a specific maximum current flows via the one transistor of the first transistor pair, and a specific non-zero minimum current flows via the other transistor of the first transistor pair.
2. A line driver for data transmission comprising a plurality of driver stages, each driver stage comprising:
a first transistor pair with first and second transistors which are differentially actuated as a function of the data which is to be transmitted; and
a second transistor pair with a first and second cascade transistor, the first cascade transistor of the second transistor pair connected in series between the first transistor of the first transistor pair of the same driver stage and a first output of the line driver, and the second cascade transistor connected in series between the second transistor of the first transistor pair of the same driver stage and a second output of the line driver, in such a way that the individual driver stages are connected in each case in parallel via the corresponding second transistor pair to the first and second outputs of the line driver;
a control circuit allocated to each driver stage for creating differential control signals (VG A , VG B ) to actuate the two transistors of the first transistor pair of the individual driver stage, whereby each control circuit is designed in such a way that, when the differential control signals (VG A , VG B ) are created, a specific maximum current flows via the one transistor of the first transistor pair, and a specific minimum current flows via the other transistor of the first transistor pair;
wherein each control circuit is designed in such a way that it can adjust the common mode level of the control signals (VG A , VG B ) created to actuate the two transistors of the first transistor pair of the individual driver stage, independently of the signal level swing of these control signals (VG A , VG B ).
3. A line driver for data transmission comprising a plurality of driver stages, each driver stage comprising:
a first transistor pair with first and second transistors which are differentially actuated as a function of the data which is to be transmitted; and
a second transistor pair with a first and second cascade transistor, the first cascade transistor of the second transistor pair connected in series between the first transistor of the first transistor pair of the same driver stage and a first output of the line driver, and the second cascade transistor connected in series between the second transistor of the first transistor pair of the same driver stage and a second output of the line driver, in such a way that the individual driver stages are connected in each case in parallel via the corresponding second transistor pair to the first and second outputs of the line driver;
a control circuit allocated to each driver stage for creating differential control signals (VG A , VG B ) to actuate the two transistors of the first transistor pair of the individual driver stage, whereby each control circuit is designed in such a way that, when the differential control signals (VG A , VG B ) are created, a specific maximum current flows via the one transistor of the first transistor pair, and a specific minimum current flows via the other transistor of the first transistor pair;
wherein each control circuit comprises a pair of transfer gates, whereby each transfer gate is actuated by complementary control signals (DW, DW′) as a function of the data which is to be transmitted, and optionally forwards, or not, a current (I sig ) from a current source as a function of the actuation by these control signals (DW, DW′), to a voltage divider formed by switching elements with a linear voltage/current characteristic curve, whereby at the one voltage divider the control signal (VG B ) is provided for the actuation of the first transistor, and at the other voltage divider the control signal (VG A ) is provided for the actuation of the second transistor of the first transistor pair of the corresponding driver stage.
4. The line driver according to claim 3 , wherein the current source is adjustable.
5. The line driver according to claim 3 , wherein the voltage dividers coupled to the transfer gates are in each case fed with the current (I CM ) from a second and third adjustable current source respectively.
6. The line driver according to claim 3 , wherein each voltage divider comprises a series circuit consisting of a first switch element with a linear voltage/current characteristic curve and a second switch element with a linear voltage/current characteristic curve, whereby at the second switch elements of the voltage dividers the control signals (VG A , VG B ) are prepared for the two transistors of the first transistor pair of the corresponding driver stage, and a node between the first switch element and the second switch element is connected to an output of the individual transfer gate in each case.
7. The line driver according to claim 6 , wherein the second switch elements of the voltage dividers allocated to the two transfer gates have identical resistance values.
8. The line driver according to claim 6 , wherein an adjustable capacitor is connected in parallel to the second switch elements of the voltage dividers in each case.
9. The line driver according to claim 6 , wherein the switch elements are capable of being adjusted with the linear voltage/current characteristic curve of the voltage dividers.
10. A line driver for data transmission comprising a plurality of driver stages, each driver stage comprising:
a first transistor pair with first and second transistors which are differentially actuated as a function of the data which is to be transmitted; and
a second transistor pair with a first and second cascade transistor, the first cascade transistor of the second transistor pair connected in series between the first transistor of the first transistor pair of the same driver stage and a first output of the line driver, and the second cascade transistor connected in series between the second transistor of the first transistor pair of the same driver stage and a second output of the line driver, in such a way that the individual driver stages are connected in each case in parallel via the corresponding second transistor pair to the first and second outputs of the line driver;
wherein the cascade transistors of the second transistor pair of each driver stage ate subjected to a bias voltage by a corresponding voltage source, which is connected to the individual cascade transistor to the second transistor pair in each case by means of a bias voltage line, whereby the bias voltage line allocated to each cascade transistor of the second transistor pair is couples to a capacitor.
11. The line driver according to claim 10 , wherein the capacitors coupled to the bias voltage lines of the cascade transistors of the second transistor pair of each driver stage ate of an order of size of 10 pF.
12. The line driver according to claim 1 , wherein the first and second outputs are adapted to be connected to line cores of a data transfer line.
13. The line driver according to claim 3 , wherein the first and second outputs are adapted to be connected to line cores of a data transfer line.
14. The line driver according to claim 13 , wherein a pulse former generates the complementary control signals (DW, DW) for the transfer gates of the control circuits of the individual driver stages.
15. The line driver according to claim 10 , further comprising a control circuit allocated to each driver stage for creating differential control signals (VG A , VG B ) to actuate the two transistors of the first transistor pair of the individual driver stage, whereby each control circuit is designed in such a way that, when the differential control signals (VG A , VG B ) are created, a specific maximum current flows via the one transistor of the first transistor pair, and a specific minimum current flows via the other transistor of the first transistor pair.
16. The line driver according to claim 15 , wherein each control circuit comprises a pair of transfer gates, whereby each transfer gate is actuated by complementary control signals (DW, DW′) as a function of the data which is to be transmitted, and optionally forwards, or not, a current (I sig ) from a current source as a function of the actuation by these control signals (DW, DW′), to a voltage divider formed by switching elements with a linear voltage/current characteristic curve, whereby at the one voltage divider the control signal (VG B ) is provided for the actuation of the first transistor, and at the other voltage divider the control signal (VG A ) is provided for the actuation of the second transistor of the first transistor pair of the corresponding driver stage.
17. The line driver according to claim 16 , wherein the current source is adjustable.
18. The line driver according to claim 16 , wherein the voltage dividers coupled to the transfer gates are in each case fed with the current (I CM ) from a second and third adjustable current source respectively.
19. The line driver according to claim 16 , wherein each voltage divider comprises a series circuit consisting of a first switch element with a linear voltage/current characteristic curve and a second switch element with a linear voltage/current characteristic curve, whereby at the second switch elements of the voltage dividers the control signals (VG A , VG B ) are prepared for the two transistors of the first transistor pair of the corresponding driver stage, and a node between the first switch element and the second switch element is connected to an output of the individual transfer gate in each case.
20. The line driver according to claim 19 , wherein the second switch elements of the voltage dividers allocated to the two transfer gates have identical resistance values.
21. The line driver according to claim 19 , wherein an adjustable capacitor is connected in parallel to the second switch elements of the voltage dividers in each case.
22. The line driver according to claim 19 , wherein the switch elements are capable of being adjusted with the linear voltage/current characteristic curve of the voltage dividers.
23. The line driver according to claim 1 , wherein the cascade transistors of the second transistor pair of each driver stage are subjected to a bias voltage by a corresponding voltage source, which is connected to the individual cascade transistor of the second transistor pair in each case by means of a bias voltage line, whereby the bias voltage line allocated to each cascade transistor of the second transistor pair is coupled to a capacitor.
24. The line driver according to claim 23 , wherein the capacitors coupled to the bias voltage lines of the cascade transistors of the second transistor pair of each driver stage are of an order of size of 10 pF.
25. The line driver according to claim 2 , wherein the cascade transistors of the second transistor pair of each driver stage are subjected to a bias voltage by a corresponding voltage source, which is connected to the individual cascade transistor of the second transistor pair in each case by means of a bias voltage line, whereby the bias voltage line allocated to each cascade transistor of the second transistor pair is coupled to a capacitor.
26. The line driver according to claim 25 , wherein the capacitors coupled to the bias voltage lines of the cascade transistors of the second transistor pair of each driver stage are of an order of size of 10 pF.