AMPLIFICATION DEVICE FOR AMPLIFYING A SIGNAL IN ELECTRO-OPTICAL TRANSCEIVERS

Abstract

An amplification device configured for amplifying a signal with a DC signal component is provided, which comprises a coupling filter circuit having an input terminal and an output terminal. The coupling filter circuit attenuates the DC signal component of an input signal to obtain a filtered output signal. The coupling filter circuit comprises a first capacitor circuit connecting the input terminal to the output terminal; a second capacitor circuit connected in parallel to the first capacitor circuit, a first resistor and a second resistor, wherein the second capacitor, the first resistor and the second resistor are serially connected; and a resistor circuit connected to the input terminal and the output terminal and comprising a third resistor connected to the input terminal and a fourth resistor connected to the output terminal. The amplification device comprises an amplification circuit connected to the output terminal, which amplifies the filtered signal.

Claims

1. An amplification device configured for amplifying a signal, the amplification device comprising: a coupling filter circuit having an input terminal for receiving an input signal and an output terminal for outputting a filtered output signal, wherein the coupling filter circuit is configured to at least attenuate a DC signal component of the input signal to obtain the filtered output signal, wherein the coupling filter circuit comprises a first capacitor circuit connecting the input terminal to the output terminal, the first capacitor circuit comprising a first capacitor; a second capacitor circuit connected in parallel to the first capacitor circuit, the second capacitor circuit comprising a second capacitor, a first resistor and a second resistor, the second capacitor, the first resistor and the second resistor being serially connected; and a resistor circuit connected to the input terminal and the output terminal, the resistor circuit comprising a third resistor connected to the input terminal and a fourth resistor connected to the output terminal; and an amplification circuit connected to the output terminal, the amplification circuit being configured to amplify the filtered signal to obtain an amplified filtered signal.

2. The amplification device according to claim 1, wherein the second capacitor circuit is connected in parallel to the first capacitor of the first capacitor circuit.

3. The amplification device according to claim 1, wherein the first capacitor circuit is composed only of the first capacitor.

4. The amplification device according to claim 1, wherein the second capacitor is connected between the first resistor and the second resistor, the first resistor being directly connected to the input terminal, the second resistor being directly connected to output terminal.

5. The amplification device according to claim 4, wherein the second capacitor circuit is composed only of the second capacitor, the first resistor and the second resistor.

6. The amplification device according to claim 1, wherein at least one of the following is true: the third resistor of the resistor circuit is arranged to couple the input terminal to a reference potential or the fourth resistor of the resistor circuit is arranged to couple the output terminal to the reference potential.

7. The amplification device according to claim 1, wherein the amplification circuit comprises or is formed by a field effect transistor having a gate terminal, wherein the output terminal is connected to the gate terminal.

8. The amplification device according to claim 1, further comprising a further coupling filter circuit, the further coupling circuit being formed identical to the coupling filter circuit, the coupling filter circuit and the further coupling filter circuit being arranged for differential mode operation.

9. The amplification device according to claim 8, comprising a further amplification circuit, arranged downstream the further coupling filter circuit.

10. The amplification device according to claim 8, wherein the further coupling filter circuit comprises a further input terminal for receiving an inverted version of the input signal, a further output terminal for outputting a further filtered output signal, and: a further first capacitor circuit connecting the further input terminal to the further output terminal, the further first capacitor circuit comprising a further first capacitor; a further second capacitor circuit connected in parallel to the further first capacitor circuit, the further second capacitor circuit comprising a further second capacitor, a further first resistor and a further second resistor, the further second capacitor, the further first resistor and the further second resistor being serially connected; and a further resistor circuit connected to the further input terminal and the further output terminal, the further resistor circuit comprising a further third resistor connected to the further input terminal and a further fourth resistor connected to the further output terminal, wherein the third resistor of the resistor circuit and the further third resistor of the further resistor circuit are electrically connected, and the coupling filter circuit is connected to the further coupling filter circuit.

11. The amplification device according to claim 10, wherein the third resistor and the further third resistor are electrically connected at a connection point, wherein the amplification device comprises a shunting capacitor connecting the connection point to a reference potential.

12. The amplification device according to claim 11, further comprising a diode circuit comprising a first diode and a second diode, the first diode and the second diode being connected antiparallel to each other in an antiparallel diode circuit that connects the connection point to a reference potential.

13. The amplification device according to claim 1, wherein the respective input terminal is connected via a shunt resistor to a reference potential.

14. The amplification device according to claim 1, wherein the respective coupling filter circuit has an electrical bandpass characteristic.

15. The amplification device according to claim 1, wherein the respective coupling filter circuit comprises integrated capacitors according to a metal-insulator-metal technology.

16. An optical receiver, comprising: an amplification device, wherein the amplification device comprises: a coupling filter circuit having an input terminal for receiving an input signal and an output terminal for outputting a filtered output signal, wherein the coupling filter circuit is configured to at least attenuate a DC signal component of the input signal to obtain the filtered output signal, wherein the coupling filter circuit comprises a first capacitor circuit connecting the input terminal to the output terminal, the first capacitor circuit comprising a first capacitor; a second capacitor circuit connected in parallel to the first capacitor circuit, the second capacitor circuit comprising a second capacitor, a first resistor and a second resistor, the second capacitor, the first resistor and the second resistor being serially connected; and a resistor circuit connected to the input terminal and the output terminal, the resistor circuit comprising a third resistor connected to the input terminal and a fourth resistor connected to the output terminal; and an amplification circuit connected to the output terminal, the amplification circuit being configured to amplify the filtered signal to obtain an amplified filtered signal; and a converter being configured to convert an optical signal into an electrical signal.

17. The amplification device according to claim 6, wherein the reference potential is a ground potential.

18. The amplification device according to claim 9, wherein the further amplification circuit comprises a further field effect transistor.

19. The amplification device according to claim 13, wherein the reference potential is a ground potential.

20. The amplification device according to claim 14, wherein the respective coupling filter circuit has a lower cut-off frequency being equal to 300 kHz with a tolerance range of +/−5% or +/−10%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Further embodiments of the invention will be described with respect to the following figures, wherein:

[0051] FIG. 1 shows a schematic diagram of a state-of-the-art integrated AC-coupled driver amplifier scheme;

[0052] FIG. 2 shows a schematic diagram of a state-of-the-art integrated AC-coupled driver amplifier scheme based on a metal-insulator-metal capacitor;

[0053] FIG. 3 shows a schematic diagram of an amplification device according to an embodiment;

[0054] FIG. 4 shows a schematic diagram of an integrated AC-coupled driver amplifier according to an embodiment;

[0055] FIG. 5 shows a schematic diagram of an amplification device according to an embodiment;

[0056] FIG. 6 shows a schematic diagram of an amplification device according to an embodiment;

[0057] FIG. 7 shows a schematic diagram of an integrated AC-coupled driver amplifier according to an embodiment in differential mode;

[0058] FIG. 8 shows a schematic diagram of an integrated AC-coupled driver amplifier comprising a shunting capacitor according to an embodiment in differential mode; and

[0059] FIG. 9 shows a schematic diagram of an integrated AC-coupled driver amplifier comprising a diode circuit according to an embodiment in differential mode.

[0060] In the various figures, identical reference signs will be used for identical or at least functionally equivalent features.

DETAILED DESCRIPTION OF EMBODIMENTS

[0061] In the following description, reference is made to the accompanying drawings, which form part of the disclosure, and in which are shown, by way of illustration, specific aspects in which the present invention may be placed. It will be appreciated that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, as the scope of the present invention is defined by the appended claims.

[0062] For instance, it will be appreciated that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if a specific method step is described, a corresponding device may include a unit to perform the described method step, even if such unit is not explicitly described or illustrated in the figures.

[0063] Moreover, in the following detailed description as well as in the claims embodiments with different functional blocks or processing units are described, which are connected with each other or exchange signals. It will be appreciated that the present invention covers embodiments as well, which include additional functional blocks or processing units that are arranged between the functional blocks or processing units of the embodiments described below.

[0064] Finally, it is understood that the features of the various exemplary aspects described herein may be combined with each other, unless specifically noted otherwise.

[0065] As will be described in more detail in the following under reference to FIGS. 3 and 4, embodiments of the invention relate to an amplification device 300 which is configured for amplifying a signal that has a DC component to be filtered.

[0066] As can be seen from FIG. 3, the amplification device 300 comprises: a coupling filter circuit 301 having an input terminal 315 for receiving the input signal and an output terminal 317 for outputting a filtered output signal, wherein the coupling filter circuit 301 is configured to at least attenuate the DC signal component of the input signal to obtain the filtered output signal.

[0067] According to an embodiment, the coupling filter circuit 301 comprises: a first capacitor circuit connecting the input terminal 315 to the output terminal 317, the first capacitor circuit comprising a first capacitor 303; and a second capacitor circuit connected in parallel to the first capacitor circuit, the second capacitor circuit comprising a second capacitor 305, a first resistor 307 and a second resistor 309, wherein the second capacitor 305, the first resistor 307 and the second resistor 309 are serially connected.

[0068] According to an embodiment, the coupling filter circuit 301 further comprises: a resistor circuit connected to the input terminal 315 and the output terminal 317, the resistor circuit comprising a third resistor 311 connected to the input terminal 315 and a fourth resistor 313 connected to the output terminal 317.

[0069] The amplification device 300 further comprises an amplification circuit 321 connected to the output terminal 317, wherein the amplification circuit 321 is configured to amplify the filtered signal to obtain an amplified filtered signal.

[0070] FIG. 4 shows a more general schematic diagram of an integrated coupling filter circuit 301 according to an embodiment, wherein the coupling filter circuit 301 comprises mainly the following components: two capacitors (C.sub.G1 303 and C.sub.G2 305); four resistors (R.sub.1 311, R.sub.2 309, R.sub.3 307 and R.sub.G 313); an input port 315 (IN) and an output port 317 (OUT).

[0071] As shown in FIGS. 3 and 4, the second capacitor circuit is connected in parallel to the first capacitor 303 of the first capacitor circuit and the first capacitor circuit is composed only of the first capacitor 303. Likewise, the second capacitor circuit is composed only of the second capacitor 305, the first resistor 307 and the second resistor 309. The second capacitor 305 is connected between the first resistor 307 and the second resistor 309, and the first resistor 307 is directly connected to the input terminal 315 and the second resistor 309 is directly connected to output terminal 317.

[0072] According to an embodiment, the third resistor 311 of the resistor circuit is arranged to couple the input terminal 315 to a reference potential, in particular to a ground potential, and/or the fourth resistor 313 of the resistor circuit is arranged to couple the output terminal 317 to a reference potential, in particular to a ground potential. Further, the amplification circuit comprises or is formed by a field effect transistor having a gate terminal, wherein the output terminal is connected to the gate terminal.

[0073] According to embodiments of the invention, the low cut-off frequency of the driver amplifier can be extended without reducing the maximum data-rate or life-time of the driver amplifier itself, through a proper choice of the values of the second capacitor C.sub.G2 305 and the first resistor R.sub.3 307 as well as the second resistor R.sub.2 309. To highlight the benefits, it is convenient to analyze the driver amplifier according to an embodiment in a low frequency range and in a high frequency range, which will be demonstrated in the following under reference to FIGS. 5 and 6.

[0074] In the low frequency range, the equivalent impedance of the second capacitor C.sub.G2 305 is much higher than the first resistor R.sub.3 307 and the second resistor R.sub.2 309. As a consequence, the proposed amplification device shown in FIG. 3 can be simplified into the amplification device 500 shown in FIG. 5, wherein the amplification device 500 comprises a coupling filter circuit 501 and an amplification circuit 503. The resulting low cut-off frequency (ω.sub.LCF) of the amplification device 500 in FIG. 5 can be estimated by using the following equation:

[00003]${\omega }_{LCF}=\frac{1}{R_G.Math.\left(C_{G1}+C_{G2}\right)}.$

[0075] Thus, assuming that the first capacitor C.sub.G1 303 is equal to the capacitor C.sub.G as in FIG. 1, the low cut-off frequency (ω.sub.LCF) of the proposed amplifier is reduced, i.e. extended, without affecting reliability margin of the driver amplifier by increasing the value of the resistor R.sub.G.

[0076] In the high frequency range, the equivalent impedance of the first capacitor C.sub.G1 303 and

[0077] the second capacitor C.sub.G2 305 is much higher than the first resistor R.sub.3 307 and the second resistor R.sub.2 309 according to an embodiment. As a consequence, the embodiment shown in FIG. 3 can be simplified into the amplification device 600 shown in FIG. 6, wherein the amplification device 600 comprises a coupling filter circuit 601 and an amplification circuit 603. The resulting high cut-off frequency (ω.sub.HFC) of the amplification device 600 in FIG. 6 can be estimated by using the following equation:

[00004]${\omega }_{HCF}=\frac{R_S+R_1}{R_S.Math.R_1.Math.\left(C_{GS}+C_{B1}\right)}$

[0078] wherein C.sub.B1 denotes the parasitic capacitor 605 to ground of the first capacitor C.sub.G1 303. From the above equation, it is to be noted that the parasitic capacitor to ground (C.sub.B2) of the second capacitor C.sub.G2 305 does not affect the high cut-off frequency of the amplification device 600.

[0079] To further demonstrate the benefits of the amplification device according to embodiments of the invention, a numerical example will be discussed in the following.

[0080] It is assumed that a driver amplifier is designed to achieve a low cut-off frequency of 1 MHz and a high cut-off frequency of 45 GHz. The resulting values of capacitors and resistors in a prior art driver amplifier are as follows: R.sub.S, R.sub.1, and R.sub.G are 50 Ohm, 50 Ohm and 50 KOhm respectively; C.sub.G, C.sub.B and C.sub.GS are 3.2 pF, 32 fF and 110 fF respectively, wherein it is assumed that the parasitic capacitor to ground of the MIM capacitor (C.sub.B) is hundred times lower than the MIM capacitor value (C.sub.G). Moreover, an input capacitance of 110 fF is assumed for the amplifier block. Finally, the output impedance of the source (R.sub.S) is assumed to be 50 Ohm.

[0081] By using the aforementioned equations in the background section, it is possible to derive 1 MHz as low cut-off frequency and 45 GHz as high cut-off frequency. It is now required to extend the low cut-off frequency of the driver amplifier to 300 KHz in order be compliant with new standard, without affecting reliability margin of the driver amplifier.

[0082] By using the prior art scheme, the only solution is to increase the MIM capacitor value (i.e. CG=10.6 pF), wherein R.sub.S, R.sub.1, and R.sub.G are 50 Ohm, 50 Ohm and 50 KOhm respectively; C.sub.G, C.sub.B and C.sub.GS are 10.6 pF, 106 fF and 110 fF respectively.

[0083] However, the parasitic capacitor to ground (C.sub.B) also increases, resulting in a reduced high frequency cut-off which is equal to 29.5 GHz.

[0084] On the contrary, the low cut-off frequency can be extended without affecting the high cut-off frequency for the embodiments of the invention. In fact, it is possible to select proper values for the second capacitor C.sub.G2 and the first resistor R.sub.3 307 as well as the second resistor R.sub.2 309 as follows: R.sub.S, R.sub.1, and R.sub.G are 50 Ohm, 50 Ohm and 50 KOhm respectively; C.sub.G, C.sub.B and C.sub.GS are 3.2 pF, 32 fF and 110 fF respectively; R.sub.2, R.sub.3, C.sub.G2, and C.sub.B2 are 3 KOhm, 3 KOhm, 7.4 pF and 74 fF respectively.

[0085] By using the above equations as discussed along with FIGS. 5 and 6, it is possible to find that the low cut-off frequency of the amplification device is extended to 300 KHz, while the high cut-off frequency is kept as the original case, i.e. equal to 45 GHz.

[0086] According to a further embodiment, FIG. 7 shows a schematic diagram of an exemplary amplification device 700, which can be used in differential-mode. As can be taken in a close view from FIG. 7, the amplification device 700 further comprises a coupling filter circuit 301 and a further coupling filter circuit 701, wherein the further coupling circuit 701 is formed identical to the coupling filter circuit 301, and the coupling filter circuit 301 and the further coupling filter circuit 701 are arranged for differential mode operation.

[0087] In an embodiment, the amplification device 700 further comprises a further amplification circuit, in particular a further field effect transistor, arranged downstream the further coupling filter circuit 701.

[0088] As in FIGS. 3 and 4, the coupling filter circuit 301 comprises: a first capacitor circuit connecting the input terminal 315 to the output terminal 317, the first capacitor circuit comprising a first capacitor 303; and a second capacitor circuit connected in parallel to the first capacitor circuit, the second capacitor circuit comprising a second capacitor 305, a first resistor 307 and a second resistor 309, wherein the second capacitor 305, the first resistor 307 and the second resistor 309 are serially connected. According to an embodiment, the coupling filter circuit 301 further comprises: a resistor circuit connected to the input terminal 315 and the output terminal 317, the resistor circuit comprising a third resistor 311 connected to the input terminal 315 and a fourth resistor 313 connected to the output terminal 317.

[0089] In a further embodiment, the further coupling filter circuit 701 comprises a further input terminal 715 for receiving an inverted version of the input signal, a further output terminal 717 for outputting a further filtered output signal.

[0090] The further coupling filter circuit 701 comprises: a further first capacitor circuit connecting the further input terminal 715 to the further output terminal 717, the further first capacitor circuit comprising a further first capacitor 703; a further second capacitor circuit connected in parallel to the further first capacitor circuit, wherein the further second capacitor circuit comprises a further second capacitor 705, a further first resistor 707 and a further second resistor 709. The further second capacitor 705, the further first resistor 707 and the further second resistor 709 are serially connected.

[0091] In an embodiment, the further coupling filter circuit 701 also comprises: a further resistor circuit connected to the further input terminal 715 and the further output terminal 717, the further resistor circuit comprising a further third resistor 711 connected to the further input terminal 715 and a further fourth resistor 713 connected to the further output terminal 717.

[0092] As seen in FIG. 7, the third resistor 311 of the resistor circuit and the further third resistor 711 of the further resistor circuit are electrically connected, thereby connecting the coupling filter circuit 301 to the further coupling filter circuit 701.

[0093] FIG. 8 shows a schematic diagram of an exemplary amplification device 800 according to an embodiment, where a capacitor (C1) is added into the amplification device 700 as shown in FIG. 7 in order to shunt a high frequency common-mode. Similar to the amplification device 700 in FIG. 7, the amplification device 800 comprises a coupling filter circuit 301 and a further coupling filter circuit 701, wherein the further coupling circuit 701 is formed identical to the coupling filter circuit 301.

[0094] In particular, the third resistor 311 and the further third resistor 711 are electrically connected at a connection point, wherein the amplification device 800 comprises a shunting capacitor 801 connecting the connection point to a reference potential, in particular to a ground potential.

[0095] FIG. 9 shows a schematic diagram of an exemplary amplification device 900 according to an embodiment, where two diodes, a first diode 901 and a second diode 903, are added into the amplification device 800 as shown in FIG. 8 in order to protect the shunting capacitor 801 from electro-static discharge.

[0096] Similar to the amplification device 700 in FIG. 7 or the amplification device 800 in FIG. 8, the amplification device 900 also comprises a coupling filter circuit 301 and a further coupling filter circuit 701, wherein the further coupling circuit 701 is formed identical to the coupling filter circuit 301.

[0097] In an embodiment, the amplification device 900 comprises a diode circuit comprising a first diode 901 and a second diode 903, wherein the first diode 901 and the second diode 903 are connected antiparallel to each other, the antiparallel diode circuit connecting the connection point to reference potential, in particular a ground potential.

[0098] In an embodiment, the respective input terminal is connected via a shunt resistor to a reference potential, in particular to a ground potential.

[0099] In an embodiment, the respective coupling filter circuit has an electrical bandpass characteristic, in particular with a lower cut-off frequency being equal to 300 kHz within a tolerance range, in particular +/−5% or +/−10%.

[0100] While a particular feature or aspect of the disclosure may have been disclosed with respect to only one of several implementations or embodiments, such feature or aspect may be combined with one or more other features or aspects of the other implementations or embodiments as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms “include”, “have”, “with”, or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprise”. Also, the terms “exemplary”, “for example” and “e.g.” are merely meant as an example, rather than the best or optimal. The terms “coupled” and “connected”, along with derivatives may have been used. It should be understood that these terms may have been used to indicate that two elements cooperate or interact with each other regardless whether they are in direct physical or electrical contact, or they are not in direct contact with each other.

[0101] Although specific aspects have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific aspects shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific aspects discussed herein.

[0102] Although the elements in the following claims are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.

[0103] Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the invention beyond those described herein. While the present invention has been described with reference to one or more particular embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the scope of the present invention. It is therefore to be understood that within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described herein.