Amplifier circuit for driving electro-optic modulator with low process, voltage and temperature (PVT) sensitivity

Abstract

The present invention relates to the field of amplifier circuits (driver amplifiers) for electro-optical modulators, and is specifically used for amplifying electrical signals to drive the electro-optical modulators. The present invention proposes an amplifier circuit for amplifying signals, the amplifier circuit comprising a gain amplifier, a distributed amplifier, a resistor and a current source, wherein the input end of the distributed amplifier is electrically connected to the output end of the gain amplifier; the resistor is terminated at the input end of the distributed amplifier; and the current source is electrically connected in parallel to the resistor. The present invention also proposes a method for setting a bias voltage of such an amplifier circuit. In addition, the present invention also proposes a transmitter (specifically an optical transmitter) comprising such an amplifier circuit and a system comprising such a transmitter and a signal source.

Description

Technical Field

[0001] The present invention relates to the field of amplifier circuits (driver amplifiers) for electro-optical modulators, in particular for amplifying electrical signals to drive said electro-optical modulators, especially in transmitters for optical communications. The general purpose of the invention is to achieve a broadband amplifier circuit (broadband driver amplifier) ​​with an optimal gain / bandwidth product and low sensitivity to process, voltage and temperature variations.

[0002] The term "process, voltage and temperature (PVT) sensitivity" may be used as a synonym for the term "sensitivity to process, voltage and temperature variations". This aspect is particularly useful for transmitters for optical communications, where a broadband amplifier circuit (a broadband driver amplifier) ​​is used to boost the level of a signal source, such as a high-speed digital source, in order to be sufficiently powered to properly drive an electro-optic modulator. To this end, the present invention provides an amplifier circuit for amplifying a signal, and also provides a method for setting a bias voltage for such an amplifier circuit. In addition, the present invention also provides a transmitter, in particular an optical transmitter, comprising such an amplifier circuit; and finally, a system comprising such a transmitter and a signal source is provided. The amplifier circuit may also be referred to as a "driver amplifier". Background Art

[0003] In most advanced optical communication transmitter schemes, it is required that the amplifier circuit (driver amplifier) ​​has a matched output impedance. The reason is that the matched output impedance of the amplifier circuit absorbs reflections from the interconnects and components between the amplifier circuit itself and the electro-optic modulator driven by the amplifier circuit. For example, such interconnects and components include bonding wires, pads, bias coils or beads, DC blocking capacitors, and feed lines.

[0004] To this end, an amplifier circuit for an optical transmitter (also referred to as a "driver amplifier for an optical transmitter") is generally implemented by cascading a gain amplifier and a distributed amplifier, wherein an input end of the distributed amplifier is electrically connected to an output end of the gain amplifier. The distributed amplifier is capable of achieving matching output impedance over a wide bandwidth. In addition, the gain amplifier is capable of achieving a target gain level.

[0005] Figure 6 FIG. 1 is an exemplary block diagram of an amplifier circuit 101 including a cascaded gain amplifier 102 and a distributed amplifier 103. An output terminal 102b of the gain amplifier 102 is electrically connected to an input terminal 103a of the distributed amplifier 103. The input terminal 103a of the distributed amplifier is finally terminated at a resistor R g On. Resistor R g It can also be called a "termination resistor". Provide a DC voltage V DDThe DC voltage source 105 can be connected to the resistor R g , used to provide a bias current I to the output terminal 102b of the gain amplifier 102 through the input terminal 103a of the distributed amplifier 103 g and bias voltage V A In other words, the DC voltage V of the DC voltage source 105 DD It is used to bias the amplifier circuit 101, and specifically to bias the gain amplifier 102 of the amplifier circuit 101. The bias voltage V at the output terminal 102b of the gain amplifier 102 A Depends on the DC voltage V DD and resistor R g .exist Figure 6 In the embodiment, the input terminal 102a of the gain amplifier 102 is connected to the input terminal 101a of the amplifier circuit 101, and the output terminal 103b of the distributed amplifier 103 is connected to the output terminal 101b of the amplifier circuit 101. A signal source such as a high-speed digital source can be connected to the input terminal 101a of the amplifier circuit 101, and an electro-optic modulator can be connected to the output terminal 101b of the amplifier circuit 101. out ” represents the parasitic output capacitance of the gain amplifier 102.

[0006] In optical transmitters, the input impedance and output impedance of the amplifier circuit are usually specified at the system level. In practice, the input impedance is defined by the signal source, such as a high-speed digital source; while the output impedance is defined by the electro-optic modulator. Therefore, the gain / bandwidth product of the amplifier circuit can be optimized by properly selecting and optimizing the input resistance of the distributed amplifier and the parasitic output capacitance of the gain amplifier, respectively. However, due to the limited bias voltage, the optimal conditions in terms of performance are more sensitive to process, voltage and temperature variations (PVT variations).

[0007] In this case, in order to maximize both product performance and yield, a solution is needed that can implement an amplifier circuit (driver amplifier) ​​with a maximum gain / bandwidth product and low sensitivity to process, voltage, and temperature variations. Summary of the invention

[0008] The embodiment of the present invention aims to improve the conventional solution to deal with the DC voltage V provided to the amplifier circuit. DDThe objective is to provide an amplifier circuit (driver amplifier) ​​having a maximum gain / bandwidth product and low sensitivity to process, voltage and temperature variations. It is beneficial to be able to simultaneously optimize the gain / bandwidth product and linearity of the amplifier circuit, thereby maximizing both performance and yield of the product.

[0009] The objects of the invention are achieved by the embodiments provided in the attached independent claims. Advantageous implementations of the embodiments are further defined in the dependent claims.

[0010] Specifically, embodiments of the present invention are based on setting a bias voltage of an amplifier circuit including a cascaded gain amplifier and a distributed amplifier, which is achieved by a resistor terminating an input of the distributed amplifier and a current source electrically connected in parallel to the resistor.

[0011] Therefore, an amplifier circuit having a maximum gain / bandwidth product and lower sensitivity to process, voltage, and temperature variations (lower process, voltage, and temperature sensitivity / PVT sensitivity) can be realized.

[0012] A first aspect of the present invention provides an amplifier circuit for amplifying a signal, wherein the amplifier circuit comprises:

[0013] -Gain amplifier;

[0014] -Distributed amplifiers;

[0015] - resistors;

[0016] - current source;

[0017] The input end of the distributed amplifier is electrically connected to the output end of the gain amplifier; the resistor is connected to the input end of the distributed amplifier; and the current source is electrically connected to the resistor in parallel.

[0018] In the amplifier circuit according to the first aspect, a current source is connected in parallel to the resistor terminating the input terminal of the distributed amplifier.

[0019] The resistor terminating the input end of the distributed amplifier may also be referred to as a “termination resistor.” Specifically, the resistor is an input matching resistor terminating the input end of the distributed amplifier.

[0020] As described below, the bandwidth and gain of the amplifier circuit and the bias voltage V provided to the output terminal of the gain amplifier A Depends on the value of the resistor.

[0021] Since the current source is electrically connected to the resistor in parallel, the current flowing through the resistor can be shunted, so that the current flowing through the resistor can be set. Specifically, the current source reduces the current flowing through the resistor. Therefore, in the amplifier circuit according to the first aspect, the nominal bias voltage V A Higher gain amplifier than conventional amplifiers with a nominal bias voltage V A .

[0022] Therefore, in the amplifier circuit according to the first aspect, the minimum bias voltage of the gain amplifier has a large margin, thereby reducing the sensitivity to process, voltage and temperature changes. In other words, the current source in the amplifier circuit increases the nominal bias voltage of the gain amplifier, so the minimum bias voltage of the gain amplifier has a large margin, thereby reducing the sensitivity to process, voltage and temperature changes of the amplifier circuit.

[0023] According to the first aspect, since the amplifier circuit has low sensitivity to process, voltage and temperature variations, the gain / bandwidth product and linearity of the amplifier circuit can be optimized simultaneously, thereby maximizing product performance and yield at the same time.

[0024] Therefore, with the amplifier circuit according to the first aspect, an amplifier circuit having a maximum gain / bandwidth product and a low sensitivity to process, voltage and temperature variations can be provided.

[0025] The resistors may be used to set the bandwidth and gain of the amplifier circuit.

[0026] A DC voltage source can be electrically connected to the resistor, and is used to provide a bias current and a bias voltage to the output end of the gain amplifier through the input end of the distributed amplifier. Specifically, the current source is used to set the bias voltage by setting a current flowing from the DC voltage source through the resistor.

[0027] In particular, the current source is used to set the current flowing through the resistor by shunting a portion of the current provided by the DC voltage source. In particular, the current source is used to set the current flowing through the resistor to a value lower than the current provided by the DC voltage source. Thus, in particular, the current source is used to reduce the voltage drop at the resistor.

[0028] Since the bias voltage (V A ) depends on the voltage drop at the resistor, for example, “(I g -I q )·R g”, the current source is used to increase the bias voltage (V A ). This is advantageous because the bias voltage V A The increase will result in a larger margin for the minimum bias voltage of the gain amplifier, thereby reducing the sensitivity of the amplifier circuit to process, voltage and temperature variations. In other words, the bias voltage V A The increase will result in increased margins for process, voltage, and temperature variations.

[0029] Specifically, the impedance of the current source is higher than the impedance of the resistor.

[0030] In particular, the current source presents a high impedance to the electrical signal to be amplified by the amplifier circuit.Thus, the gain and bandwidth of the amplifier circuit are independent of the current source.

[0031] The current source in the amplifier circuit increases the bias voltage of the gain amplifier, so the minimum bias voltage of the gain amplifier has a large margin, thereby reducing the process, voltage and temperature variation sensitivity of the amplifier circuit. At the same time, specifically, the current source exhibits high impedance, so it will not affect the gain and bandwidth of the amplifier circuit.

[0032] Furthermore, specifically, the impedance of the current source is set to a certain size so that it does not have a substantial impact on the gain and bandwidth of the amplifier circuit.

[0033] In other words, specifically, the impedance of the current source is set to a certain magnitude so that the gain and bandwidth of the amplifier circuit do not depend on the current source.

[0034] In an implementation manner of the first aspect, specifically, the current source includes a transistor, and the transistor is used to set the current flowing through the resistor.

[0035] This provides an efficient and low-cost solution for implementing the current source.

[0036] Specifically, the transistor is used to set the current flowing from the DC voltage source through the resistor so that at least one third of the bias current flows through the resistor.

[0037] Specifically, the transistor of the current source is a field effect transistor, specifically a metal oxide semiconductor field effect transistor or a bipolar transistor.

[0038] According to a specific alternative, specifically, the transistor of the current source is a field effect transistor, wherein the source terminal and the gate terminal of the field effect transistor are electrically connected to the terminals of the resistor, and the terminals of the resistor are electrically connected to the input of the distributed amplifier; the drain terminal is electrically connected to the other terminal of the resistor, and the DC voltage source can be electrically connected to the other terminal of the resistor.

[0039] According to another specific alternative, specifically, the transistor of the current source is a bipolar transistor, wherein the emitter terminal and the base terminal of the bipolar transistor are electrically connected to the terminals of the resistor, and the terminals of the resistor are electrically connected to the input of the distributed amplifier; the collector terminal is electrically connected to the other terminal of the resistor, and the DC voltage source can be electrically connected to the other terminal of the resistor.

[0040] In particular, the amplifier circuit is used to be implemented in an integrated circuit, in particular a monolithic microwave integrated circuit.

[0041] A second aspect of the present invention provides a transmitter, specifically an optical transmitter, comprising the amplifier circuit according to the first aspect or any implementation thereof, as described above. Specifically, the transmitter is a transmitter for optical communication.

[0042] In an implementation of the second aspect, specifically, the transmitter includes: an electro-optic modulator for generating an optical signal; wherein the electro-optic modulator is electrically connected to an output end of the amplifier circuit, specifically, an output end of a distributed amplifier of the amplifier circuit; wherein the amplifier circuit is used to amplify a signal to drive the electro-optic modulator. In other words, specifically, in the transmitter, the amplifier circuit is used to amplify an electrical signal to drive the electro-optic modulator.

[0043] The third aspect of the present invention provides a system, comprising: a transmitter according to the second aspect or any implementation thereof, as described above; a signal source electrically connected to the input of an amplifier circuit, specifically electrically connected to the input of a gain amplifier of the amplifier circuit.

[0044] Specifically, the signal source is used to provide an electrical signal to the input end of the amplifier circuit to drive the electro-optic modulator. Specifically, the signal source is a digital source, specifically a high-speed digital source.

[0045] In an implementation of the third aspect, specifically, the system includes: a DC voltage source electrically connected to the resistor, the resistor being connected to an input end of a distributed amplifier of the amplifier circuit. Specifically, the DC voltage source is connected to the resistor, and is used to provide a bias current and a bias voltage to the output end of the gain amplifier of the amplifier circuit through the input end of the distributed amplifier of the amplifier circuit.

[0046] A fourth aspect of the present invention provides a method for setting a bias voltage of an amplifier circuit according to the first aspect or any implementation thereof, the method comprising:

[0047] The current sunk by the current source of the amplifier circuit from a DC voltage source connected to a resistor of the amplifier circuit is set so as to set a current flowing from the DC voltage source through the resistor, thereby setting the bias voltage.

[0048] It should be noted that all devices, elements, units and modules described in this application can be implemented by software or hardware elements or any type of combination thereof. All steps performed by various entities described in this application and the functions described by various entities are intended to indicate that the corresponding entities are used to perform the corresponding steps and functions. Although in the description of the following specific embodiments, the specific functions or steps performed by the external entity are not embodied in the description of the specific detailed elements of the entity performing the specific steps or functions, it should be clear to the technician that these methods and functions can be implemented by corresponding software or hardware elements or any combination thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In conjunction with the accompanying drawings, the following description of specific embodiments illustrates the various aspects and implementation methods of the present invention described above.

[0050] Figure 1 FIG. 1 shows a block diagram of an amplifier circuit provided by an embodiment of the present invention, wherein the amplifier circuit has a bias voltage V for setting a gain amplifier of the amplifier circuit. A A current source;

[0051] FIG2(a) shows an exemplary Figure 1 The embodiment shown provides a gain / bandwidth product of an amplifier circuit, wherein a nominal DC voltage V is provided to the amplifier circuit. DD ;

[0052] FIG2(b) shows an exemplary Figure 1 The total harmonic distortion (THD) of the amplifier circuit provided by the embodiment shown is Figure 1The illustrated embodiment provides a relationship between the peak-to-peak output voltage (VOUTpp) of an amplifier circuit, wherein a nominal DC voltage V is provided to the amplifier circuit. DD ;

[0053] FIG2(c) shows an exemplary Figure 1 The embodiment shown provides a gain / bandwidth product of an amplifier circuit, wherein a process angle DC voltage V is provided to the amplifier circuit. DD ;

[0054] FIG2(d) shows an exemplary Figure 1 The total harmonic distortion (THD) of the amplifier circuit provided by the embodiment shown is Figure 1 The embodiment shown provides a relationship between the peak-to-peak output voltage (VOUTpp) of the amplifier circuit, wherein a process angle DC voltage V is provided to the amplifier circuit. DD ;

[0055] Figure 3 FIG. 1 shows a block diagram of an amplifier circuit provided by an embodiment of the present invention, wherein the amplifier circuit has a bias voltage V for setting a gain amplifier of the amplifier circuit. A Current sources (including transistors);

[0056] Figure 4 A block diagram of a transmitter provided by an embodiment of the present invention is shown, wherein the transmitter includes an amplifier circuit provided by an embodiment of the present invention;

[0057] Figure 5 A block diagram of a system provided by an embodiment of the present invention is shown, wherein the system includes a transmitter provided by an embodiment of the present invention;

[0058] Figure 6 An exemplary block diagram of an amplifier circuit including a cascaded gain amplifier and a distributed amplifier is shown;

[0059] FIG. 7( a ) shows an exemplary Figure 6 The gain / bandwidth product of the amplifier circuit shown in FIG. 1 , wherein the amplifier circuit is provided with a nominal DC voltage V DD ;

[0060] FIG. 7( b ) shows an example of Figure 6 The total harmonic distortion (THD) of the amplifier circuit shown in Figure 6 The relationship between the peak output voltage (VOUTpp) of the amplifier circuit shown in FIG. 1 , wherein the amplifier circuit is provided with a nominal DC voltage V DD ;

[0061] FIG. 7( c ) shows an exemplary Figure 6 The gain / bandwidth product of the amplifier circuit shown in FIG. 1 , wherein a process angle DC voltage V is provided to the amplifier circuit DD ;

[0062] FIG. 7( d ) shows an exemplary Figure 6 The total harmonic distortion (THD) of the amplifier circuit shown in Figure 6 The relationship between the peak output voltage (VOUTpp) of the amplifier circuit shown in FIG. 1 and the process angle DC voltage V DD . DETAILED DESCRIPTION

[0063] Some considerations that lay the foundation for embodiments of the present invention are described in detail below. The bandwidth of an amplifier circuit used in a transmitter for optical communications is typically a specification bandwidth derived from a target bit rate of an optical communications standard. Figure 6 The exemplary block diagram of the amplifier circuit 101 is shown in FIG. 1 , by appropriately selecting the terminating resistor R g The value of can achieve the target bandwidth with maximum gain. In fact, the bandwidth of the amplifier circuit 101 can be approximately expressed by the following equation:

[0064]

[0065] Among them, "C out ” is the parasitic output capacitance of the gain amplifier 102. Therefore, the parasitic output capacitance C out The value of the resistor R g to achieve the target bandwidth. g After the value of , the gain of the amplifier circuit 101 can be defined according to the following equation:

[0066] Gain ≈ A V_DA ·G m_GA ·R g (2)

[0067] Among them, "A V_DA ” is the voltage gain of the distributed amplifier 103, “G m_GA ” is the transconductance gain of the gain amplifier 102. At the same time, the bias voltage V of the gain amplifier 102 can also be defined according to the following equation: A :

[0068] V A =V DD -I g ·R g (3)

[0069] In summary, the termination resistor R can be selected according to the above equations (1) and (2): g The value of , in order to optimize the gain / bandwidth product according to the requirements of the optical communication standard. However, the selection can also determine the bias voltage V of the gain amplifier 102 according to the above equation (3): A In other words, the terminating resistor R g The optimal value of will affect the DC bias condition of the gain amplifier 102, making the gain amplifier 102 and therefore the amplifier circuit 101 very sensitive to process, voltage and temperature variations (PVT variations).

[0070] Considering equation (3), it can be noted that if the bias current I g due to process or temperature variations, or if the DC voltage V provided to the amplifier circuit for biasing the amplifier circuit is DD Due to the voltage change, the bias voltage V of the gain amplifier 102 decreases. A The bias current I g increases due to process or temperature variations, or if the DC voltage V DD Due to the voltage change, the bias voltage V of the gain amplifier 102 decreases. A The external operating conditions of the gain amplifier 102 can be reduced.

[0071] If this problem occurs, you can reduce the termination resistor R g Therefore, the nominal bias voltage V of the gain amplifier 102 is A Increasing (see equation (3)) results in a larger margin with respect to process, temperature, and voltage variations, and thus reduces the sensitivity to process, voltage, and temperature variations.

[0072] However, due to the reduction of the termination resistor R g The gain of the amplifier circuit 101 will also decrease as shown in the above equation (2). Therefore, the optimal gain / bandwidth product cannot be achieved.

[0073] In order to better illustrate the problems of the traditional solution, that is, to reduce the termination resistor R g The value of Figure 7(a) to Figure 7(d)The typical performance of an amplifier circuit including a cascade of a gain amplifier and a distributed amplifier is shown in FIG. 1 , wherein the output of the gain amplifier is connected to the input of the distributed amplifier, and the input of the distributed amplifier is connected to the Figure 6 The amplifier circuit 101 shown in FIG. 1 is a terminating resistor R g superior.

[0074] FIG7(a) shows the gain / bandwidth product, where a nominal DC voltage V is supplied to the amplifier circuit. DD , used to bias the amplifier circuit; wherein the vertical axis represents the gain (S21) of the amplifier circuit, in dB; the horizontal axis represents the frequency, in GHz. FIG7(b) shows the relationship between the total harmonic distortion (THD) of the amplifier circuit and the peak-to-peak output voltage (VOUTpp) of the amplifier circuit, wherein a nominal DC voltage V is provided to the amplifier circuit DD , used to bias the amplifier circuit; wherein the vertical axis represents the total harmonic distortion (THD) of the amplifier circuit, in percentage (%); the horizontal axis represents the peak-to-peak output voltage (VOUTpp) of the amplifier circuit, in volts (V).

[0075] FIG7(c) shows the gain / bandwidth product, where a DC voltage V is supplied to the amplifier circuit. DD The process angle value is shown in Figure 7(d), wherein the vertical axis represents the gain (S21) of the amplifier circuit in dB, and the horizontal axis represents the frequency in GHz. Figure 7(d) shows the relationship between the total harmonic distortion (THD) of the amplifier circuit and the peak-to-peak output voltage (VOUTpp) of the amplifier circuit, wherein a DC voltage V is provided to the amplifier circuit. DD The process angle value of the amplifier circuit is shown in Figure 1, wherein the vertical axis represents the total harmonic distortion (THD) of the amplifier circuit in percentage (%); the horizontal axis represents the peak-to-peak output voltage (VOUTpp) of the amplifier circuit in volts (V). The DC voltage V DD The process angle value is less than the DC voltage V DD Nominal value.

[0076] Assume that the target bandwidth of the amplifier circuit is 30 GHz, as shown by the vertical dashed lines in Figures 7(a) and 7(c). To achieve the best gain / bandwidth product, the termination resistor R gA value such as 55 ohms is selected to obtain a gain (S21) of 30 dB, as shown by the solid line in FIG7(a). When the terminating resistor R is set to 100 Ω for the purpose of achieving the best gain / bandwidth product, the gain (S21) of 30 dB is obtained. g When a value such as 55 ohms is selected, the total harmonic distortion (THD) of the amplifier circuit is shown as the solid line in FIG7(b). Assuming that the THD target is that the THD must be less than 3% of the peak-to-peak output voltage (VOUTpp) up to 4.5V, as shown by the horizontal dashed lines in FIG7(b) and FIG7(d). These performances shown in FIG7(a) and FIG7(b) are at a nominal DC voltage VOUTpp such as 3.3V. DD The DC voltage V is provided to the amplifier circuit. DD , to provide a bias current I to the gain amplifier of the amplifier circuit g and bias voltage V A By providing the nominal DC voltage V DD , the amplifier circuit (specifically the gain amplifier of the amplifier circuit) is appropriately biased. Under this "nominal" condition, assuming that the bias current I of the gain amplifier g is 20mA (example), the bias voltage V A is 2.2V, so assuming that the value of the nominal DC voltage is equal to 3.3V, the terminating resistor R g The value of is equal to 55 ohms (see equation (3) above).

[0077] However, due to voltage variation, the process corner DC voltage V DD can drop to 3V, causing the gain amplifier bias voltage V A is only equal to 1.9V (see equation (3) above), which is lower than the minimum bias voltage for normal operation of the gain amplifier. In other words, the gain amplifier can no longer be properly biased, and therefore the amplifier circuit can no longer be properly biased. Under this "process corner" condition, the gain (S21) of the amplifier circuit becomes the solid line shown in Figure 7(c), and the THD becomes the solid line shown in Figure 7(d) (assuming that the termination resistor is maintained at a value such as 55 ohms to achieve the best gain / bandwidth product). As shown in Figure 7(d), under the "process corner" condition, the THD (as shown by the solid line) exceeds the above target for the THD because the THD is no less than 3% of the peak-to-peak output voltage (VOUTpp) of up to 4.5V.

[0078] In order to solve the DC voltage V DD Change (the DC voltage V DDThe problem is caused by the nominal value of the termination resistor R g For example, choose the termination resistor R g , making it equal to a value such as 45 ohms (instead of the previously assumed 55 ohms), so that under the above-mentioned "process corner" conditions (V DD =3V), the THD of the amplifier circuit is again within the above target range of the THD, as shown by the dotted line in FIG7(d). That is, in FIG7(d), for the terminating resistor R g The dotted line showing the THD is up to VOUTpp=4.5V below the dotted line showing the target THD.

[0079] Referring to the above equation (3), in the terminating resistor R g The value drops to 45 ohms at the “process corner” condition (V DD =3V), the bias voltage V A =2.1V (assuming I g =20mA), the gain amplifier will be properly biased. However, due to the terminating resistor R g The value of decreases, the gain (S21) of the amplifier circuit decreases by about 1 dB, as shown in FIG. 7( a ). DD The dotted line and the process angle DC voltage V DD At the same time, the nominal DC voltage V is provided to the amplifier circuit. DD When the terminating resistor R g The reduced value of will deteriorate the THD behavior of the amplifier circuit, as shown by the dotted line in Figure 7(b).

[0080] The performance comparison of the amplifier circuit has proved that the above solution proposed in the prior art (reducing the terminating resistor R g value) to deal with the DC voltage V DD Considering the process, voltage and temperature variations, it is impossible to optimize the Figure 6 The gain / bandwidth product and linearity of an amplifier circuit such as the amplifier circuit shown in . The linearity of the amplifier circuit depends on the bias of the amplifier circuit.

[0081] Figure 1The block diagram of the amplifier circuit 101 (driver amplifier) ​​provided by the embodiment of the present invention is shown. The amplifier circuit 101 includes a gain amplifier 102 and a distributed amplifier 103. The gain amplifier 102 is used to amplify the electrical signal to its input terminal 102a to a target gain level. The distributed amplifier 103 is used to achieve matching output impedance of the amplifier circuit 101 within a certain broadband range.

[0082] The embodiments of the present invention are not limited to a specific gain amplifier, and therefore, any gain amplifier known to those skilled in the art can be used to implement the gain amplifier 102. The same applies to the distributed amplifier 103, and therefore, any distributed amplifier known to those skilled in the art can be used to implement the distributed amplifier 103.

[0083] The input terminal 103a of the distributed amplifier 103 is electrically connected to the output terminal 102b of the gain amplifier 102. Therefore, the gain amplifier 102 and the distributed amplifier 103 are cascaded in the amplifier circuit 101. The input terminal 102a of the gain amplifier 102 is connected to the input terminal 101a of the amplifier circuit 101, and the output terminal 103b of the distributed amplifier 103 is connected to the output terminal 101b of the amplifier circuit 101.

[0084] The amplifier circuit 101 further includes a resistor R g , the resistor R g The input terminal 103a of the distributed amplifier 103 is terminated. Figure 1 The input terminal 103a of the distributed amplifier 103 and the resistor R g The resistor Rg can also be called a "termination resistor". Specifically, the resistor R g is an input matching resistor terminating the input terminal 103 a of the distributed amplifier 103 .

[0085] according to Figure 1 , the resistor R g is not part of the distributed amplifier 103. Alternatively, the resistor R g It can be a part of the distributed amplifier 103.

[0086] like Figure 1 As shown, the DC voltage source 105 can be electrically connected to the resistor R g The DC voltage source 105 provides a DC voltage V DD, used to bias the amplifier circuit 101, specifically used to bias the gain amplifier 102. In other words, the DC voltage source 105 can be electrically connected to the resistor R g , used to provide a bias current I to the output end 102b of the gain amplifier 102 through the input end 103a of the distributed amplifier 103 g and bias voltage V A Specifically, the DC voltage source 105 can be connected to the resistor R g The input terminal 103a of the distributed amplifier 103 is connected to the resistor R g The other terminal N1.

[0087] The amplifier circuit 101 also includes a resistor R g The current source 104 is used to set the current from the DC voltage source 105 to flow through the resistor R g The current is used to set the bias voltage V A .

[0088] according to Figure 1 , the current source 104 is not a part of the distributed amplifier 103 . Alternatively, the current source 104 may be a part of the distributed amplifier 103 .

[0089] The current source 104 is used to pass the resistor R g Divide the current I provided by the DC voltage source 105 g part, to set the current flowing through the resistor R g Specifically, the current source 104 is used to convert the current flowing through the resistor R g The current is set to be lower than the current I provided by the DC voltage source 105 g The current source 104 is used to reduce the current flowing through the resistor R g The current is used to reduce the resistor R g The pressure drop at .

[0090] like Figure 1 As shown, the bias current I for biasing the gain amplifier 102 g does not flow completely through the resistor R g , but partially flows through the current source 104.

[0091] Specifically, the impedance of the current source 104 is higher than the resistor R gThe impedance of the current source 104 is 0.04. Therefore, the current source 104 presents a high impedance to the signal applied to the input terminal 101a of the amplifier circuit 101. Therefore, the gain and bandwidth of the amplifier circuit 101 are independent of the current source 104. The above equation (1) applies to the bandwidth of the amplifier circuit 101, and the above equation (2) applies to the gain of the amplifier circuit 101.

[0092] Since the current source 104 is electrically connected in parallel to the resistor R g , so that the current flowing through the resistor can be shunted, and thus the current flowing from the DC voltage source 105 through the resistor R g Specifically, the current source 104 can reduce the current flowing through the resistor R g Therefore, according to Figure 1 In the amplifier circuit 101 shown, the nominal bias voltage V of the gain amplifier 102 is A Higher than Figure 6 The gain of the amplifier circuit shown in the figure is the nominal bias voltage of the amplifier, as applied to Figure 1 The amplifier circuit 101 shown in equation (4) is as follows:

[0093] V A =V DD -(I g -I q )·R g (4)

[0094] For the above equation (4), assume that a DC voltage source is connected to the resistor to provide a DC voltage V DD , used to bias the amplifier circuit, specifically used to bias the gain amplifier. In equation (4), “I q " represents the currents respectively diverted by the current source 104; "I g -I q ” indicates the current flowing through the resistor R g (terminating resistor) current; "I g " represents the bias current provided to the output terminal 102b of the gain amplifier 102; "V A ” represents a bias voltage provided to the output terminal 102 b of the gain amplifier 102.

[0095] More suitable for Figure 1 The amplifier circuit shown in equation (4) is similar to the amplifier circuit not equipped with a current source (such as Figure 6 When considering equation (3) of the amplifier circuit shown in FIG. 1 , the following can be noted:

[0096] according to Figure 1 The nominal bias voltage V of the gain amplifier 102 of the amplifier circuit 101 is shown. A (See equation (4)) is higher than the amplifier circuit without current source (such as Figure 6 The amplifier circuit shown in the figure) has a gain amplifier with a nominal bias voltage V A (See equation (3)). In other words, in the amplifier circuit 101 shown in accordance with 1, the current Ig flowing through the terminating resistor R is greater than the current Ig flowing through the terminating resistor of the amplifier circuit not equipped with a current source connected in parallel to the terminating resistor. g The current I g -I q The reduction is the current I diverted by the current source 104. q .

[0097] Therefore, according to Figure 1 In the amplifier circuit 101 shown, the minimum bias voltage of the gain amplifier has a large margin, thereby reducing the sensitivity to process, voltage and temperature variations. In other words, Figure 1 The current source 104 in the amplifier circuit 101 shown in FIG. 1 increases the bias voltage V of the gain amplifier 102. A Therefore, the minimum bias voltage of the gain amplifier 102 has a large margin, thereby reducing the sensitivity of the amplifier circuit 101 to process, voltage and temperature changes.

[0098] At the same time, the current source 104 presents a high impedance to the signal that may be provided to the input terminal 101a of the amplifier circuit 101. Therefore, the gain and bandwidth of the driver amplifier 101 are independent of the current source 104.

[0099] Therefore, if Figure 1 As shown in equation (4), one aspect of the embodiment of the present invention is to connect the current source 104 in parallel to the resistor R connected to the input terminal 103a of the distributed amplifier 103. g The current source 104 reduces the current flowing through the resistor R g The current is used to reduce the resistor R g This will increase the bias voltage V of the gain amplifier 102. A , thereby reducing the process, voltage and temperature variation sensitivity of the amplifier circuit 101. At the same time, the current source 104 does not affect the signal that can be provided to the input terminal 101a of the amplifier circuit 101 because the current source exhibits a high impedance.

[0100] Specifically, the current source 104 includes a transistor, which is used to set the current flowing through the resistor (R g )( Figure 1 Not shown, Figure 3 However, as long as the current can be g Divide the current I provided by the DC voltage source 105 g part to set (specifically reduce) the current flowing through the resistor R g The current source 104 can also be implemented in different ways.

[0101] Specifically, the amplifier circuit 101 is used to be implemented in an integrated circuit (specifically a monolithic microwave integrated circuit).

[0102] Specifically, select the resistor R g The value of is used to optimize the gain / bandwidth product of the amplifier circuit 101.

[0103] In order to better explain the Figure 1 The advantages of the amplifier circuit 101 are shown in Figure 2(a) to Figure 2(d) Shown according to Figure 1 The performance of the amplifier circuit 101 is shown.

[0104] FIG2(a) shows an exemplary Figure 1 The embodiment shown provides a gain / bandwidth product of an amplifier circuit, wherein a nominal DC voltage V is provided to the amplifier circuit. DD Figure 2(b) shows an example of Figure 1 The total harmonic distortion (THD) of the amplifier circuit provided by the embodiment shown is Figure 1 The illustrated embodiment provides a relationship between the peak-to-peak output voltage (VOUTpp) of an amplifier circuit, wherein a nominal DC voltage V is provided to the amplifier circuit. DD .

[0105] FIG2(c) shows an exemplary Figure 1 The embodiment shown provides a gain / bandwidth product of an amplifier circuit, wherein a process angle DC voltage V is provided to the amplifier circuit. DD Figure 2(d) shows an example of Figure 1 The total harmonic distortion (THD) of the amplifier circuit provided by the embodiment shown is Figure 1 The embodiment shown provides a relationship between the peak-to-peak output voltage (VOUTpp) of the amplifier circuit, wherein a process angle DC voltage V is provided to the amplifier circuit. DD .

[0106] In FIG. 2(a) and FIG. 2(c), the vertical axis represents the gain (S21) of the amplifier circuit in dB, and the horizontal axis represents the frequency in GHz. In FIG. 2(b) and FIG. 2(d), the vertical axis represents the total harmonic distortion (THD) of the amplifier circuit in percentage (%), and the horizontal axis represents the peak-to-peak output voltage (VOUTpp) of the amplifier circuit in volts (V).

[0107] The Figure 1 The performance of the amplifier circuit 101 is shown to be 3.3V nominal DC voltage V provided by the DC voltage source 105. DD The DC voltage source 105 can be connected to Figure 1 The terminating resistor R of the amplifier circuit 101 shown in g Therefore, the nominal voltage V selected in FIG. 2(a) and FIG. 2(b) is DD Corresponding to the nominal voltage V selected in FIG. 7( a ) and FIG. 7( b ) DD .

[0108] In FIG. 2(a) and FIG. 2(c), it is assumed that the target bandwidth of the amplifier circuit 101 is 30 GHz, as indicated by the vertical dashed lines in FIG. 2(a) and FIG. 2(c). This target bandwidth corresponds to the target bandwidth assumed in FIG. 7(a) and FIG. 7(c) above. In order to achieve the optimal gain / bandwidth product, Figure 1 The terminating resistor R of the amplifier circuit 101 shown in g Choose a value such as 55 ohms and achieve Figure 1 The current sources 104 of the amplifier circuit 101 shown in the figure are configured to absorb a current I of, for example, 4 mA. q This will result in a gain (S21) of 30 dB, as shown by the solid line in FIG2(a). Therefore, the gain of the amplifier circuit provided according to the present invention is the same as the gain of the amplifier circuit without the current source, as shown by the solid line in FIG7(a). In other words, Figure 1 The current source 104 of the amplifier circuit 101 shown in FIG. 1 is high impedance, so the current source 104 does not affect Figure 1 The gain and bandwidth of the amplifier circuit 101 shown in FIG. 1 do not have any effect.

[0109] according to Figure 1The total harmonic distortion (THD) of the amplifier circuit 101 under "nominal" conditions is shown as the solid line in FIG. 2(b). Assume that the THD target is that the THD must be lower than 3% of the peak-to-peak output voltage (VOUTpp) of up to 4.5V (THD < 3% of the peak-to-peak output voltage of up to 4.5V), as shown by the horizontal dashed lines in FIG. 2(b) and FIG. 2(d). As shown by the solid line in FIG. 2(b) and the solid line in FIG. 7(b), under "nominal" conditions (a nominal DC voltage VOUTpp of, for example, 3.3V is provided to the amplifier circuit), the total harmonic distortion (THD) of the amplifier circuit 101 under "nominal" conditions (a nominal DC voltage VOUTpp of, for example, 3.3V is provided to the amplifier circuit) is shown as the solid line in FIG. 2(b) and the solid line in FIG. 7(b) DD ), Figure 1 The performance of the amplifier circuit 101 in terms of THD is comparable to that of an amplifier circuit without a current source (eg Figure 6 The amplifier circuit shown in FIG. 1 has the same performance in terms of THD.

[0110] The Figure 1 The performance of the amplifier circuit 101 is shown at a process voltage V of 3V provided by the DC voltage source 105. DD The DC voltage source 105 can be connected to Figure 1 The terminating resistor R of the amplifier circuit 101 shown in g Therefore, the Figure 1 The performance of the amplifier circuit 101 shown corresponds to the process corner voltage V DD Corresponding to the process corner voltage V based on FIG. 7( c ) and FIG. 7( d ) DD .

[0111] When the “process corner” condition is considered, a reduced DC voltage V such as 3V is provided to the amplifier circuit. DD hour, Figure 1 The amplifier circuit 101 shown in FIG. 2 allows achieving better THD, which meets the specification (THD < 3% of the peak-to-peak output voltage up to 4.5V), as shown by the solid line in FIG. 2( d ). This is because according to the following equation (4):

[0112] V A =V DD -(I g -I q )·R g

[0113] Assuming the following conditions, Figure 1 The nominal bias voltage V of the gain amplifier 102 of the amplifier circuit 101 shown in FIG. A Equals 2.42V:

[0114] - The nominal DC voltage V DD Equal to 3.3V;

[0115] - the bias current I of the gain amplifier g Equal to 20mA;

[0116] - The current I diverted by the current source 104 q Equal to 4mA;

[0117] - The terminating resistor R g The value of is equal to 55 ohms to achieve the best gain / bandwidth product.

[0118] Therefore, due to the current source 104, compared with an amplifier circuit not equipped with a current source (such as Figure 6 The amplifier circuit shown in the figure) has a gain amplifier with a nominal bias voltage V A compared to, Figure 1 The nominal bias voltage V of the gain amplifier 102 of the amplifier circuit 101 shown in FIG. A Therefore, according to Figure 1 In the amplifier circuit 101 shown, the minimum bias voltage of the gain amplifier has a large margin, thereby reducing the sensitivity to process, voltage and temperature variations.

[0119] In other words, according to equation (3):

[0120] V A =V DD -I g ·R g

[0121] This applies to amplifier circuits that are not equipped with a current source (such as Figure 6 The amplifier circuit shown in FIG. 1 is shown in FIG. 1 . When the following conditions are assumed, the nominal bias voltage V of the gain amplifier is A Only equal to 2.2V:

[0122] - The nominal DC voltage V DD Equal to 3.3V;

[0123] - the bias current I of the gain amplifier g Equal to 20mA;

[0124] - The terminating resistor R g The value of is equal to 55 ohms to achieve the best gain / bandwidth product.

[0125] Therefore, under the “process angle” condition, when the DC voltage V DD When the process angle value drops to 3V, Figure 1The bias voltage V of the gain amplifier 102 of the amplifier circuit 101 shown in FIG. A from 2.42V (“nominal” condition) to 2.12V (“corner” condition). The 2.12V reduced bias voltage V A Still within the operating range of the gain amplifier, therefore, Figure 1 The gain amplifier 102 of the amplifier circuit 101 shown in FIG. 1 is appropriately biased under the “process corner” condition. In other words, as described above, due to Figure 1 The nominal bias voltage V of the gain amplifier 102 of the amplifier circuit 101 is shown. A Increase, the minimum bias voltage of the gain amplifier has a larger margin, thereby reducing the sensitivity of process, voltage and temperature changes. Therefore, under the "process corner" condition, Figure 1 The THD of the amplifier circuit 101 shown in FIG. 2 is less than 3% of the peak-to-peak output voltage (VOUTpp) up to 4.5V, as shown by the solid line in FIG. 2( d ).

[0126] In contrast, under the “process angle” condition, when the DC voltage V DD When the process corner value drops to 3V, the amplifier circuit without current source (such as Figure 6 The amplifier circuit shown in FIG. 1 is a gain amplifier with a bias voltage V A from 2.2V (“nominal” condition) to 1.9V (“corner” condition) (see equation (3)). This reduced bias voltage V A is no longer within the operating range of the gain amplifier, and therefore, the gain amplifier is not properly biased. Therefore, under the "process corner" condition, the THD exceeds the THD target, as shown by the solid line in Figure 7(d). In other words, as shown in Figure 7(d), under the "process corner" condition, the THD exceeds the THD target (for example, when the termination resistor R g The value of 55 ohms is used to achieve the best gain / bandwidth product), because the THD is not lower than 3% of the peak-to-peak output voltage (VOUTpp) up to 4.5 V. The solid line in Figure 7(d) is not lower than the horizontal dashed line of the peak-to-peak output voltage up to 4.5 V.

[0127] In summary, if Figure 2(a) to Figure 2(d) As shown, by implementing the amplifier circuit provided according to the present invention, as Figure 1 The amplifier circuit 101 shown in FIG. 1 can simultaneously optimize the gain / bandwidth product and the linearity of the amplifier circuit in consideration of process, voltage, and temperature variations.

[0128] In summary, for an amplifier circuit not equipped with a current source, such as Figure 6 The amplifier circuit shown in the figure allows the implementation of an amplifier circuit with lower process, voltage and temperature (PVT) sensitivity without compromising other key performances such as DC power consumption, gain, bandwidth, output return loss, input return loss, circuit complexity, integrability and required bias voltage.

[0129] Figure 3 The block diagram of the amplifier circuit 101 provided in the embodiment of the present invention is shown. Figure 1 The amplifier circuit 101 shown in FIG. Similarly, Figure 1 and Figure 3 The same elements in the drawings have the same reference numerals and functions.

[0130] exist Figure 3 In the amplifier circuit 101 shown in FIG. 1 , the current source 104 includes a transistor Q1, which is specifically implemented as a transistor Q1. The transistor Q1 is used to set the current flowing through the resistor R g Specifically, the transistor Q1 is used as a current source. Specifically, the transistor Q1 is used to set the current flowing from the DC voltage source 105 through the resistor R g current, so that at least one third of the bias current I g flows through the resistor R g .

[0131] like Figure 3 As shown, the transistor Q1 of the current source 104 is a field effect transistor, specifically a metal oxide semiconductor field effect transistor. The source terminal S and the gate terminal G of the field effect transistor Q1 are electrically connected to the resistor R g terminal N1, the resistor R g The terminal N1 of the distributed amplifier 103 is electrically connected to the input terminal 103a of the distributed amplifier 103. The drain terminal D is electrically connected to the resistor R g The other terminal N2 of the DC voltage source 105 can be electrically connected to the resistor R g The other terminal N2.

[0132] The implementation of the transistor Q1 is not limited to Figure 3 For example, the transistor Q1 may also be a bipolar transistor ( Figure 3 In this case, specifically, the emitter terminal and the base terminal of the bipolar transistor will be electrically connected to the resistor R g terminal N1, the resistor R gThe terminal N1 of the distributed amplifier 103 is electrically connected to the input terminal 103a of the distributed amplifier 103. Specifically, the collector terminal of the bipolar transistor is electrically connected to the resistor R g The other terminal N2 of the DC voltage source can be electrically connected to the resistor R g The other terminal N2.

[0133] Specifically, the size of the transistor Q1 is selected to achieve the bias voltage V of the gain amplifier 102 A Required margin with respect to process, voltage, and temperature variations.

[0134] Figure 3 The amplifier circuit 101 shown in FIG. 1 is advantageous because it is a simple and inexpensive method to fully integrate an amplifier circuit according to the present invention in integrated circuit technology, in particular monolithic microwave integrated circuit technology.

[0135] Figure 4 4 shows a block diagram of a transmitter 406 provided in an embodiment of the present invention. The transmitter 406 includes the amplifier circuit 101 as described above, that is, Figure 1 and Figure 3 Specifically, the transmitter 406 is an optical transmitter, which is a transmitter used for optical communication.

[0136] The transmitter 406 further includes an electro-optic modulator 407 for generating an optical signal. The present invention is not limited to a specific electro-optic modulator, and therefore any modulator known to those skilled in the art may be used to implement the modulator 407. The electro-optic modulator 407 is electrically connected to the output terminal 101b of the amplifier circuit 101, specifically, to the output terminal 103b of the distributed amplifier 103 of the amplifier circuit 101.

[0137] The amplifier circuit 101 is used to amplify the electrical signal provided to its input terminal 101 a to drive the electro-optic modulator 407 .

[0138] Figure 5 4 shows a block diagram of a system 508 provided by an embodiment of the present invention. The system 508 includes the terminal 406 as described above, that is, Figure 4 shown.

[0139] The system further comprises a signal source 509, which is electrically connected to the input end 101a of the amplifier circuit 101 of the terminal 406. Specifically, the signal source 509 is electrically connected to the input end 102a of the gain amplifier 102 of the amplifier circuit 101. Specifically, the signal source 509 is a digital source, specifically a high-speed digital source.

[0140] The signal source 509 is used to provide an electrical signal to the input terminal 101a of the amplifier circuit 101 (specifically, to the input terminal 102a of the gain amplifier 102) to drive the electro-optical modulator 407 connected to the output terminal 101b of the amplifier circuit 101. The electrical signal provided from the signal source 509 is amplified by the amplifier circuit 101 and then output to the electro-optical modulator 407 through the output terminal 101b, so that the electro-optical modulator 407 is driven by the amplified electrical signal.

[0141] The system further comprises a DC voltage source 105 which is electrically connected to the resistor R g , the resistor R g The DC voltage source 105 is used to provide a DC voltage V to the amplifier circuit 101. DD , used to provide a bias current I to the output end 102b of the gain amplifier 102 through the input end 103a of the distributed amplifier 103 g and bias voltage V A . Connected in parallel to the resistor R g The current source 104 is used to set the DC voltage source 105 to flow through the resistor R g current, and therefore sets the resistor R g The bias voltage V of the gain amplifier 102 is set by the voltage drop at A .

[0142] The invention has been described in conjunction with various embodiments and implementations as examples. However, from a study of the drawings, the invention and the independent claims, a person skilled in the art will be able to understand and implement other variations when implementing the claimed invention. In the claims and in the specification, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" does not exclude a plurality. A single element or other unit may fulfil the functions of several entities or items listed in the claims. The listing of measures in mutually different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation.

[0143] List of reference numerals and symbols

[0144] 101 Amplifier Circuit (Driver Amplifier)

[0145] 101a Input of amplifier circuit

[0146] 101b Output of amplifier circuit

[0147] 102 Gain Amplifier

[0148] 102a Gain amplifier input

[0149] 102b Gain amplifier output

[0150] 103 Distributed Amplifier

[0151] 103a Input of distributed amplifier

[0152] 103b Output of distributed amplifier

[0153] C out Parasitic output capacitance of the gain amplifier

[0154] R g Resistors that terminate the input terminals of distributed amplifiers (termination resistors)

[0155] N1, N2 are resistor terminals that terminate the input of the distributed amplifier.

[0156] 104 Current Source

[0157] I q Current source current

[0158] Q1 Transistor

[0159] S Source terminal of the field effect transistor

[0160] D Drain terminal of the FET

[0161] G Gate terminal of the field effect transistor

[0162] 105 DC voltage source

[0163] V DD The DC voltage provided by the DC voltage source

[0164] I g The bias current supplied to the output of the gain amplifier

[0165] V A The bias voltage supplied to the output of the gain amplifier

[0166] 406 Launcher

[0167] 407 Electro-optical modulator

[0168] 508 System

[0169] 509 Signal Source

Claims

1. An amplifier circuit (101) for amplifying a signal, It is characterized in that The amplifier circuit (101) comprises: - Gain amplifier (102); - distributed amplifier (103); - Resistor (R g ); - a current source (104); wherein - the input end (103a) of the distributed amplifier (103) is electrically connected to the output end (102b) of the gain amplifier (102); - The resistor (R g ) is connected to the input terminal (103a) of the distributed amplifier (103), and the resistor (R g ) having another terminal (N2) electrically connected to a DC voltage source (105); - the current source (104) is electrically connected in parallel to the resistor (R g ), the current source (104) is used to flow from the DC voltage source (105) through the resistor (R g ) current to set the bias voltage (V A ).

2. The amplifier circuit (101) according to claim 1, It is characterized in that - The resistor (R g ) is used to set the bandwidth and gain (S21) of the amplifier circuit (101).

3. The amplifier circuit (101) according to claim 1, It is characterized in that - the amplifier circuit (101) further comprises the DC voltage source (105), the DC voltage source (105) being electrically connected to the resistor (R g ), for providing a bias current (I g ) and the bias voltage (V A ).

4. The amplifier circuit (101) according to claim 3, It is characterized in that - the impedance of the current source (104) is higher than that of the resistor (R g ) impedance.

5. The amplifier circuit (101) according to claim 4, It is characterized in that The current source (104) comprises a transistor (Q1) for setting the current flowing through the resistor (R g ) current.

6. The amplifier circuit (101) according to claim 5, It is characterized in that - the transistor (Q1) is used to set the DC voltage source (105) to flow through the resistor (R g ) current, so that at least one-third of the bias current (I g ) flows through the resistor (R g ).

7. The amplifier circuit (101) according to claim 5, It is characterized in that - The transistor (Q1) of the current source is a metal oxide semiconductor field effect transistor or a bipolar transistor.

8. The amplifier circuit (101) according to claim 5, It is characterized in that - the transistor (Q1) of the current source is a field effect transistor; - The source terminal (S) and gate terminal (G) of the field effect transistor are electrically connected to the resistor (R g ) terminal (N1), the resistor (R g ) is electrically connected to the input end (103a) of the distributed amplifier (103); - The drain terminal (D) is electrically connected to the resistor (R g ) of the other terminal (N2), the DC voltage source (105) is electrically connected to the resistor (R g ) of the other terminal (N2).

9. The amplifier circuit (101) according to claim 5, It is characterized in that - the transistor of the current source is a bipolar transistor; - The emitter terminal and the base terminal of the bipolar transistor are electrically connected to the resistor (R g ) terminal (N1), the resistor (R g ) is electrically connected to the input end (103a) of the distributed amplifier (103); - The collector terminal is electrically connected to the resistor (R g ) of the other terminal (N2), the DC voltage source (105) is electrically connected to the resistor (R g ) of the other terminal (N2).

10. The amplifier circuit (101) according to any one of claims 1 to 9, It is characterized in that - The amplifier circuit (101) is adapted to be implemented in an integrated circuit.

11. A transmitter (406), It is characterized in that include: - An amplifier circuit (101) according to any one of claims 1 to 10.

12. The transmitter (406) according to claim 11, It is characterized in that Also includes: - an electro-optic modulator (407) for generating an optical signal, - wherein the electro-optic modulator (407) is electrically connected to the output end (103b) of the distributed amplifier (103) of the amplifier circuit (101) via the output end (101b) of the amplifier circuit (101); - wherein the amplifier circuit (101) is used to amplify a signal to drive the electro-optic modulator (407).

13. A system (508), It is characterized in that include: - a transmitter (406) according to claim 11 or 12; - a signal source (509) electrically connected to an input terminal (102a) of a gain amplifier (102) of the amplifier circuit (101) via an input terminal (101a) of the amplifier circuit (101).

14. A method for setting a bias voltage (V A ) method, It is characterized in that The method comprises: - setting a current source (104) of the amplifier circuit (101) from a resistor (R g ) in order to set the current absorbed by the DC voltage source (105) to flow from the DC voltage source (105) through the resistor (R g ) current, thereby setting the bias voltage (V A ).

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