Amplifier device with variable gain and amplifier device with two inputs

Abstract

A variable gain amplifier (4) comprises: a splitter (11) for splitting a target gain signal into two signals and for outputting one signal and another signal contained in the two signals; a first variable gain amplifier (12) for amplifying one signal according to first variable gain characteristics and for outputting the one amplified signal to a first gain element (21), wherein the first variable gain amplifier (12) has the first variable gain characteristics, the gain of which is expressed by a first sigmoid function according to a control signal indicating a magnitude of an envelope of the target gain signal;and a second variable-gain amplifier (13) to amplify the other signal in accordance with second variable-gain characteristics and to output the other amplified signal to a second amplifying element (22), wherein the second variable-gain amplifier (13) has the second variable-gain characteristics, the gain of which, corresponding to the control signal, is expressed by a second sigmoid function. Furthermore, the variable-gain amplifying device (4) includes a characteristic curve setting unit (14) to set one or more gains under a gain of the first sigmoid function and a gain of the second sigmoid function as a function of a frequency of the target amplification signal.

Description

AREA OF TECHNOLOGY

[0001] The present disclosure relates to a variable gain amplifier and a dual-input amplifier. STATE OF THE ART

[0002] There is a variable gain amplification device comprising a splitter that splits an amplification target signal into two signals and outputs one split signal and the other split signal, a first variable gain amplifier that amplifies one split signal and outputs one amplified signal to a first amplification element, and a second variable gain amplifier that amplifies the other split signal and outputs the other amplified signal to a second amplification element.

[0003] As such a variable-gain amplifier, patent literature 1 discloses, for example, a variable-gain amplifier in which both a first variable-gain amplifier and a second variable-gain amplifier have variable gain characteristics, wherein a gain corresponding to a control signal indicating the magnitude of an envelope of a target gain signal is expressed by a sigmoid function to implement highly efficient operation. The variable-gain amplifier includes adjustment means for setting the variable gain characteristics to achieve a wider range of a target gain signal.Setting the variable gain properties includes setting a gain range for the variable gain properties and setting the shift of a curve that displays the variable gain properties. REFERENCE LIST PATENT LITERATURE

[0004] Patent Literature 1: JP H2-100406 A SUMMARY OF THE INVENTIONAL PROBLEM

[0005] The variable gain amplification device disclosed in patent literature 1 has the problem that the variable gain amplification device cannot obtain variable gain characteristics to implement a highly efficient operation depending on the frequency of a target amplification signal, even if a gain range or similar variable gain characteristics are set.

[0006] The present disclosure was carried out to solve the above problem, and one objective of the present disclosure is to provide a variable gain amplifier device that can achieve a wider band of a target gain signal than that of the variable gain amplifier device disclosed in patent literature 1. SOLUTION TO THE TASK

[0007] A variable-gain amplifier device according to the present disclosure comprises: a splitter for splitting a target amplification signal into two signals and for outputting one signal and the other signal contained in the two signals; a first variable-gain amplifier for amplifying one signal in accordance with first variable-gain characteristics and for outputting the one amplified signal to a first amplification element, wherein the first variable-gain amplifier has the first variable-gain characteristics, the gain of which is expressed by a first sigmoid function according to a control signal indicating a magnitude of an envelope of the target amplification signal;a second variable-gain amplifier to amplify the other signal in accordance with second variable-gain characteristics and to output the other amplified signal to a second amplifying element, wherein the second variable-gain amplifier has the second variable-gain characteristics, the gain of which, corresponding to the control signal, is expressed by a second sigmoid function; and a unit for adjusting the characteristics to set one or more gains under a gain of the first sigmoid function and a gain of the second sigmoid function depending on a frequency of the amplification target signal. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0008] According to the present disclosure, it is possible to achieve a wider band of an amplification target signal than with a variable amplification device as described in patent literature 1. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a circuit diagram showing an amplification device with two inputs including an amplification device 4 with variable gain according to embodiment 1. Fig. Figure 2 is an explanatory view showing how the gain of a first amplifier 12 with variable gain changes with respect to a control signal x when a coefficient k1 of a first sigmoid function f1(x) is fitted. Fig. Figure 3 is an explanatory view illustrating how the gain of the first variable-gain amplifier 12 changes with respect to the control signal x when a coefficient k2 of the first sigmoid function f1(x) is fitted. Fig. Figure 4 is an explanatory view illustrating how the gain of the first variable-gain amplifier 12 changes with respect to the control signal x when a coefficient k3 of the first sigmoid function f1(x) is fitted. Fig. Figure 5 is an explanatory view illustrating how the gain of the first variable-gain amplifier 12 changes with respect to the control signal x when a coefficient k4 of the first sigmoid function f1(x) is fitted. Fig. Figure 6 is a circuit diagram showing the interior of the first variable gain amplifier 12 of the variable gain amplifier device 4 according to embodiment 1. Fig. Figure 7 is a circuit diagram showing the interior of a first amplifier 12 with variable gain of an amplifier device 4 with variable gain according to embodiment 2. Fig. Figure 8 is a circuit diagram showing the interior of a first amplifier 12 with variable gain of an amplifier device 4 with variable gain according to embodiment 3. Fig. Figure 9 is a circuit diagram showing the interior of a first amplifier 12 with variable gain of an amplifier device 4 with variable gain according to embodiment 4. DESCRIPTION OF THE EXAMPLES OF EXECUTION

[0009] The following describes methods for carrying out the present disclosure with reference to the accompanying drawings, in order to further explain the present disclosure. Example 1.

[0010] Fig. Figure 1 is a circuit diagram showing an amplification device with two inputs including an amplification device 4 with variable gain according to embodiment 1.

[0011] The in Fig. The amplification device shown in Figure 1 with two inputs comprises the amplification device 4 with variable gain and an amplifier 20 with two inputs.

[0012] The variable gain amplifier device 4 comprises a splitter 11, a first variable gain amplifier 12, a second variable gain amplifier 13 and a characteristic curve setting unit 14.

[0013] The amplifier 20 with two inputs comprises a first amplification element 21 and a second amplification element 22.

[0014] An input terminal 1 receives frequency information specifying the frequency of an external amplification target signal.

[0015] An input terminal 2 receives the amplification target signal from outside.

[0016] An input terminal 3 receives an external control signal. The control signal specifies the magnitude of an envelope of the gain target signal applied to input terminal 2.

[0017] The splitter 11 splits the amplification target signal present at input terminal 2 into two signals.

[0018] The splitter 11 outputs one signal of the two split signals to the first amplifier 12 with variable gain and the other signal to the second amplifier 13 with variable gain.

[0019] The first amplifier 12 with variable gain has first variable gain properties or a first variable gain characteristic, the gain of which is expressed by a first sigmoid function according to a control signal.

[0020] The first amplifier 12 with variable gain amplifies the one signal output by the splitter 11 according to the first variable gain characteristic and outputs the one amplified signal to the first amplification element 21.

[0021] The second amplifier 13 with variable gain amplifies the other signal output by the splitter 11 according to second variable gain properties or a second variable gain characteristic and outputs the other amplified signal to the second amplification element.

[0022] An amplitude ratio, which is a ratio of the amplitude of one signal output from splitter 11 to the first amplifier 12 with variable gain and the amplitude of the other signal output from splitter 11 to the second amplifier 13 with variable gain, is also expressed by a sigmoid function.

[0023] The characteristic curve setting unit 14 records the frequency information entered at the input terminal 1.

[0024] The characteristic curve setting unit 14 sets one or more gains, namely a gain of the first sigmoid function, which indicates the first variable gain characteristics of the first variable gain amplifier 12, and a gain of the second sigmoid function, which indicates the second variable gain characteristics of the second variable gain amplifier 13, depending on the frequency of the gain target signal, which is indicated by the frequency information.

[0025] Although it is sufficient for the characteristic curve setting unit 14 to set one or more gains below the gain of the first sigmoid function and the gain of the second sigmoid function, the characteristic curve setting unit 14 can set any gain.

[0026] The in Fig. The variable gain amplifier device 4 shown in Figure 1 is described under the assumption that the characteristic curve setting unit 14 sets each gain.

[0027] The first amplification element 21 amplifies the signal amplified by the first amplifier 12 with variable gain.

[0028] The second amplification element 22 amplifies the other signal, which is amplified by the second amplifier 13 with variable gain.

[0029] A synthesis signal of one signal, which is amplified by the first amplification element 21, and of the other signal, which is amplified by the second amplification element 22, is output at an output terminal 23.

[0030] Fig. Figure 2 is an explanatory view illustrating how the gain of the first variable-gain amplifier 12 changes with respect to a control signal x when a coefficient k1 of a first sigmoid function f1(x) expressed in the following equation (1) is fitted.

[0031] The first sigmoid function f1(x) is a function that indicates how the amplitude P1 of the signal applied to the first amplifier 12 with variable gain changes depending on the control signal x. Adjusting the coefficient k1 of the first sigmoid function f1(x) corresponds to adjusting or setting a gain range of the first variable gain characteristics.

[0032] Fig. Figure 3 is an explanatory view illustrating how the gain of the first variable-gain amplifier 12 changes with respect to the control signal x when a coefficient k2 of the first sigmoid function f1(x), expressed in equation (1) below, is adjusted. Adjusting the coefficient k2 of the first sigmoid function f1(x) corresponds to adjusting, or setting, the gain of the first sigmoid function f1(x).

[0033] Fig. Figure 4 is an explanatory view illustrating how the gain of the first variable-gain amplifier 12 changes with respect to the control signal x when a coefficient k3 of the first sigmoid function f1(x), expressed in equation (1) below, is adjusted. Adjusting the coefficient k3 of the first sigmoid function f1(x) corresponds to adjusting it by shifting a curve that specifies the first variable-gain properties, or the first variable-gain characteristic.

[0034] Fig. Figure 5 is an explanatory view illustrating how the gain of the first variable-gain amplifier 12 changes with respect to the control signal x when a coefficient k4 of the first sigmoid function f1(x), expressed in equation (1) below, is adjusted. Adjusting the coefficient k4 of the first sigmoid function f1(x) corresponds to adjusting it by shifting a curve that specifies the first variable-gain properties, or the first variable-gain characteristic.

[0035] The Fig. Figures 2 to 5 show the change in the gain of the first amplifier 12 with variable gain, and the change in the gain of the second amplifier 13 with variable gain is also shown in the Fig. Figures 2 to 5 are shown. The second sigmoid function f2(x), which indicates that the amplitude P2 of the signal fed to the second amplifier 13 with variable gain changes depending on the control signal x, is expressed in the following equation (2).

[0036] Furthermore, an amplitude ratio R, which is a ratio between the amplitude P1 of the signal given by the splitter 11 to the first amplifier 12 with variable gain and the amplitude P2 of the signal given by the splitter 11 to the second amplifier 13 with variable gain, is also expressed by a sigmoid function, as given in the following equation (3). P1=f1(x)G⋅Pin=(k11+exp(−(k2x−k3))+k4)G⋅Pin P2=f2(x)G⋅Pin=(k11+exp(−(k2x−k3))+1−k4)G⋅Pin R=P1P1+P2=f1(x)f1(x)+f2(x) Pin=P1+P2

[0037] In equations (1) to (4), G represents the total gain of the first amplifier 12 with variable gain and the second amplifier 13 with variable gain, and P in represents the amplitude of a gain target signal that is fed to input terminal 2.

[0038] Fig. Figure 6 is a circuit diagram showing the interior of the first variable-gain amplifier 12 of the variable-gain amplifier 4 according to embodiment 1. The interior of the second variable-gain amplifier 13 is the same as that of the first variable-gain amplifier 12, and therefore a circuit diagram showing the interior of the second variable-gain amplifier 13 is omitted.

[0039] The first amplifier 12 with variable gain comprises a resistor 31, a power supply 32, a first control signal amplifier 33, a power supply 40, a first gain target signal amplifier 41 and a power supply 46.

[0040] In the case of the second amplifier 13 with variable gain, the one in Fig. 6 shown first control signal amplifier 33 a second control signal amplifier, and the one in Fig. The first amplification target signal amplifier shown in Figure 6, 41, is a second amplification target signal amplifier.

[0041] The first control signal amplifier 33 comprises a variable current source circuit 34, a transistor 35, a resistor 36 and transistors 37, 38 and 39.

[0042] The first amplification target signal amplifier 41 comprises a resistor 42 and transistors 43, 44 and 45.

[0043] One end of resistor 31 is connected to the input terminal 3 and to a base terminal of transistor 37.

[0044] The other end of the resistance 31 is connected to a positive side of the energy supply 32.

[0045] The positive side of the energy supply 32 is connected to the other end of the resistance 31.

[0046] The negative side of energy supply 32 is connected to the Earth.

[0047] The first control signal amplifier 33 amplifies a control signal based on the coefficient k2 set by the characteristic curve setting unit 14 and outputs the amplified control signal to the first amplification target signal amplifier 41.

[0048] The variable current source circuit 34 outputs a current I ref_k2, which corresponds to the coefficient k2 set by the characteristic curve setting unit 14, to a collector terminal and a base terminal of the transistor 35.

[0049] The collector terminal of transistor 35 is connected to an output side of the variable current source circuit 34, the base terminal of transistor 35 and a base terminal of transistor 39.

[0050] One emitter terminal of transistor 35 is connected to ground.

[0051] The base terminal of transistor 35 is connected to the output side of the variable current source circuit 34, the collector terminal of transistor 35 and the base terminal of transistor 39.

[0052] One end of resistor 36 is supplied with a voltage Vcc.

[0053] The other end of resistor 36 is connected to a collector terminal of transistor 37 and a base terminal of transistor 43.

[0054] The base terminal of transistor 37 is connected to the input terminal 3 and one end of resistor 31.

[0055] The collector terminal of transistor 37 is connected to the other end of resistor 36 and the base terminal of transistor 43.

[0056] Each emitter terminal of transistor 37 is connected to an emitter terminal of transistor 38 and a collector terminal of transistor 39.

[0057] One base terminal of transistor 38 is connected to the positive side of the power supply 40.

[0058] One collector terminal of transistor 38 is supplied with the voltage Vcc.

[0059] The emitter terminal of transistor 38 is connected to the emitter terminal of transistor 37 and the collector terminal of transistor 39.

[0060] The base terminal of transistor 39 is connected to the base terminal of transistor 35, the collector terminal of transistor 35 and the output side of the variable current source circuit 34.

[0061] The collector terminal of transistor 39 is connected to the emitter terminal of transistor 37 and the emitter terminal of transistor 38, respectively.

[0062] One emitter terminal of transistor 39 is connected to ground.

[0063] The first gain target signal amplifier 41 amplifies the one signal output by the splitter 11 in accordance with the gain corresponding to the control signal amplified by the first control signal amplifier 33, and outputs the one amplified signal to the first gain element 21.

[0064] One end of resistor 42 is supplied with the voltage Vcc.

[0065] The other end of resistor 42 is connected to a collector terminal of transistor 43 and an output terminal V. out tied together.

[0066] The base terminal of transistor 43 is connected to the other end of resistor 36 and the collector terminal of transistor 37.

[0067] The collector terminal of transistor 43 is connected to the other end of resistor 42 and the output terminal V. out tied together.

[0068] One emitter terminal of transistor 43 is connected to the emitter terminal of transistor 44 and the collector terminal of transistor 45.

[0069] One base terminal of transistor 44 is connected to the positive side of the power supply 46.

[0070] One collector terminal of transistor 44 is supplied with the voltage Vcc.

[0071] The emitter terminal of transistor 44 is connected to the emitter terminal of transistor 43 and the collector terminal of transistor 45.

[0072] One base terminal of transistor 45 is connected to an input terminal V in connected. The input port V in receives the signal output by splitter 11.

[0073] The collector terminal of transistor 45 is connected to the emitter terminal of transistor 43 and the emitter terminal of transistor 44.

[0074] One emitter terminal of transistor 45 is connected to ground.

[0075] The positive side of the power supply 46 is connected to the base terminal of transistor 44.

[0076] The negative side of energy supply 46 is related to mass.

[0077] Next, the functionality of the in Fig. The amplifier device with two inputs shown in Figure 1 is described.

[0078] The splitter 11 detects an amplification target signal present at input terminal 2.

[0079] The splitter 11 splits the amplification target signal into two signals.

[0080] The splitter 11 outputs one signal of the two split signals to the first amplifier 12 with variable gain and the other signal to the second amplifier 13 with variable gain.

[0081] Upon receiving the one signal from the splitter 11, the first amplifier 12 with variable gain amplifies the one signal according to the first variable gain characteristics and outputs the one amplified signal to the first amplification element 21.

[0082] Upon receiving the other signal from the splitter 11, the second amplifier 13 with variable gain amplifies the other signal according to the second variable gain characteristics and outputs the other amplified signal to the second amplification element 22.

[0083] The characteristic curve setting unit 14 records the frequency information entered at the input terminal 1.

[0084] The characteristic curve setting unit 14 sets a gain of the first sigmoid function f1(x), which indicates the first variable gain properties or the first variable gain characteristic of the first amplifier 12 with variable gain as a function of the frequency of the gain target signal, which is specified by the frequency information.

[0085] Furthermore, the characteristic curve setting unit 14 sets a gain of the second sigmoid function f2(x), which indicates the second variable gain properties or the second variable gain characteristic of the second amplifier 13 with variable gain as a function of the frequency of the gain target signal, which is specified by the frequency information.

[0086] The variable gain amplification device disclosed in patent literature 1 includes adjusting means for adjusting each of the coefficients k1, k3, and k4 of the sigmoid function, which define the variable gain characteristics. However, the adjusting means cannot adjust the coefficient k2 of the sigmoid function. Furthermore, the adjusting means cannot simultaneously adjust all coefficients k1, k3, and k4 of the sigmoid function.

[0087] The following describes the gain setting of the first sigmoid function f1(x), which is performed by the characteristic curve setting unit 14. It should be noted that the gain setting of the second sigmoid function f2(x), which is performed by the characteristic curve setting unit 14, is the same as the gain setting of the first sigmoid function f1(x), and therefore the description of this function is omitted.

[0088] For example, the current I is stored in an internal memory of the characteristic curve setting unit 14. ref_k2 corresponding to the coefficient k2 of the first sigmoid function f1(x) and the current I ref_k2 stored according to the coefficient k2 of the second sigmoid function f2(x).

[0089] A current I 39 The current flowing from the collector terminal to the emitter terminal of transistor 39 is dependent on the current I ref_k2The current I is determined by the variable current source circuit 34, since transistor 35 and transistor 39 form a current mirror. 39 is the sum of a current I 37 , which flows from the collector terminal to the emitter terminal of transistor 37, and a current I 38 , which flows from the collector terminal to the emitter terminal of transistor 38. Therefore, the current I 39 as expressed in the following equation (5). I39=I37+I38

[0090] A voltage difference between a base voltage of transistor 37 and a base voltage of transistor 38 is determined as a function of V cnt , a control signal given to input terminal 3, and both the current I 37 as well as the current I 38 change according to the change of V cnt .

[0091] While the current I 37 and the current I 38each according to the change of V cnt change, the current remains I 39 even when V is changed cnt constant.

[0092] When the characteristic curve setting unit 14 then detects the current I ref_k2 When the current changes, it also changes. 37 The current I 37 changes essentially linearly when the absolute value of V cnt is small. The slope of the linear characteristic curve of the current I 37 changes depending on the current I ref_k2 That is, the slope of the linear characteristic curve of the current I 37 changes depending on the coefficient k2.

[0093] If the current I 37 A voltage V flows through resistor 36 cnt_core applied to the base terminal of transistor 43. The voltage V cnt_core in a case where the absolute value of the voltage V Vcnt is small, as expressed in the following equation (6).

[0094] The voltage V cnt_core changes linearly depending on V cnt , as expressed in equation (6), and a slope of the voltage V cnt_core changes depending on the current I ref_k2 , as expressed in equation (6). Vcnt_core(Vcnt)=−RL⋅βIref_k24⋅Vcnt+(VCC−RL⋅βIref_k22)

[0095] In equation (6) R L for the resistance value of resistor 36 and β for the current mirror ratio of transistor 35 and transistor 39.

[0096] A voltage difference between the base voltage of transistor 43 and the base voltage of transistor 44 is determined depending on the voltage V. cnt_core determined, and both the current I 43 as well as the current I 44 change depending on the change in voltage V cnt_core .

[0097] One at the input port V inThe incoming signal is split between transistor 43 and transistor 44. Since the collector terminal of transistor 44 is short-circuited, the signal split to transistor 44 is not output at the output terminal V. out output. Accordingly, the output V out The signal to be output is a signal split towards the side of transistor 43.

[0098] The signal flowing through transistor 43 is amplified proportionally to the magnitude of the current flowing through transistor 43, the current depending on a voltage V. cnt_rf The voltage between the base terminals is determined. The voltage between the base terminals is V. cnt_rf is a voltage difference between the base voltage of transistor 43 and the base voltage of transistor 44. Therefore, the amplitude P1 (=G rf (V cnt_rf)) of the first amplifier 12 with variable gain as expressed in the following equation (7). G rf stands for the amplification of the first amplifier 12 with variable gain.

[0043] P1=Grf(Vcnt_rf)=RL⋅g11+exp(−(Vcnt_rf / VT)) VT=kTq

[0099] In equation (7) and equation (8), g1 represents the transconductance or transconductance of the transistor 45 V. T for the thermoelectric voltage, k for the Boltzmann constant, T for the absolute temperature and q for the electronic charge.

[0100] Equation (7) shows that the first variable gain properties or the first variable gain characteristic of the first amplifier 12 with variable gain can be determined by changing the voltage between the base terminals V cnt_rf become a sigmoid function.

[0101] Here, the slope of the linear characteristic curve of the voltage between the base terminals V changes. cnt_rfin relation to V cnt depending on the current I ref_k2 .

[0102] If the absolute value of V cnt Since it is small, the first control signal amplifier amplifies 33 V. cnt linearly according to the amplification factor-R L *βl ref_k2 / 4. Therefore, the amplitude P1 expressed in equation (7) is expressed by the following equation (9). P1=Grf(Vcnt)=RL⋅g11+exp(−(−RL⋅βIref_k24⋅Vcnt / VT))

[0103] Consequently, the characteristic curve setting unit 14 sets the coefficient k2 of the first sigmoid function f(x), so that it is possible to adjust the gain of the first variable gain characteristic curve or the first variable gain properties of the first amplifier 12 with variable gain.

[0104] That is, if V cnt When the control signal is applied to input terminal 3, the characteristic curve setting unit 14 sets the current I ref_k2according to the coefficient k2 of the first sigmoid function f(x) such that, as in Fig. Figure 3 shows that the gain of the first amplifier 12 with variable gain corresponding to the frequency of the target signal is a desired gain. The characteristic curve adjustment unit 14 controls the variable current source circuit 34 for adjusting the current I. ref_k2 .

[0105] The first amplifying element 21 amplifies the amplified signal when it receives the signal amplified by the first amplifier 12 with variable gain.

[0106] The second amplifying element 22 amplifies the other amplified signal when it receives the other signal amplified by the second amplifier 13 with variable gain.

[0107] A synthesis signal is output at output terminal 23, consisting of one signal amplified by the first amplification element 21 and the other signal amplified by the second amplification element 22.

[0108] According to the above embodiment 1, the variable gain amplifier 4 comprises: the splitter 11, which splits a target gain signal into two signals and outputs one split signal and the other split signal; the first variable gain amplifier 12, which has the first variable gain characteristic or the first variable gain properties, the gain of which is expressed by the first sigmoid function according to the control signal that specifies the magnitude of the envelope of the target gain signal, which amplifies one signal according to the first variable gain characteristic or the first variable gain properties and outputs the one amplified signal to the first amplification element 21; and the second variable gain amplifier 13, which has the second variable gain characteristic or the first variable gain properties.The second variable gain device 4 has a gain characteristic corresponding to the control signal, the gain of which is expressed by the second sigmoid function. This second sigmoid function amplifies the other signal according to the second variable gain characteristic or the second variable gain characteristics and outputs the amplified signal to the second amplification element 22. Furthermore, the variable gain amplification device 4 includes a characteristic curve setting unit 14, which sets one or more gains below the gain of the first sigmoid function and the gain of the second sigmoid function depending on the frequency of the target gain signal. Consequently, the variable gain amplification device 4 can achieve a wider range of the target gain signal than the variable gain amplification device disclosed in patent literature 1. Example 2.

[0109] In embodiment 2, an amplification device 4 with variable amplification is described, in which a characteristic curve setting unit 14 adjusts the coefficient k2 of the first and second sigmoid functions and additionally the coefficient k1 of the first and second sigmoid functions.

[0110] The configuration of a two-input amplifier including the variable gain amplifier 4 according to embodiment 2 is the same as the configuration of the two-input amplifier including the variable gain amplifier 4 according to embodiment 1, and a circuit diagram showing the two-input amplifier including the variable gain amplifier 4 according to embodiment 2 is Fig. 1.

[0111] Fig. Figure 7 is a circuit diagram showing the interior of a first amplifier 12 with variable gain of the amplifier device 4 with variable gain according to embodiment 2. It should be noted that in Fig. 7 the same reference symbols as in Fig. 6 identical or corresponding parts are designated, therefore a detailed description is omitted.

[0112] The interior of a second amplifier 13 with variable gain is the same as the interior of the first amplifier 12 with variable gain, and therefore the circuit diagram showing the interior of the second amplifier 13 with variable gain is omitted.

[0113] The first amplifier 12 with variable gain comprises the resistor 31, the power supply 32, the first control signal amplifier 33, the power supply 40, the first gain target signal amplifier 41, the power supply 46 and a first gain adjustment circuit 47.

[0114] In the case of the second amplifier 13 with variable gain, the in Fig. 7 first gain adjustment circuit shown 47 the second gain adjustment circuit.

[0115] The first gain adjustment circuit 47 comprises a variable current source circuit 48 and a transistor 49.

[0116] The first gain adjustment circuit 47 sets the amplitude of a control signal amplified by the first control signal amplifier 33 based on the coefficient k1 set by the characteristic curve adjustment unit 14. The coefficient k1 is a coefficient for setting the gain range of the first variable gain characteristic.

[0117] The variable current source circuit 48 outputs a current I ref_k1 , which corresponds to the coefficient k1 set by the characteristic curve setting unit 14, to a collector terminal and a base terminal of the transistor 49.

[0118] The collector terminal of transistor 49 is connected to an output side of the variable current source circuit 48, the base terminal of transistor 49, the base terminal of transistor 45 and V in tied together.

[0119] One emitter terminal of transistor 49 is connected to ground.

[0120] The base terminal of transistor 49 is connected to the output side of the variable current source circuit 48, the collector terminal of transistor 49, the base terminal of transistor 45 and V in tied together.

[0121] Next, the operation of the two-input amplifier according to embodiment 2 will be described. Since the components, with the exception of the characteristic curve setting unit 14 and the first gain setting circuit 47, are the same as those of the two-input amplifier according to embodiment 1, the functions of the characteristic curve setting unit 14 and the first gain setting circuit 47 will be described in detail below.

[0122] For example, the current I is stored in an internal memory of the characteristic curve setting unit 14. ref_k2 , which corresponds to the coefficient k2 of the first sigmoid function f1(x), and the current I ref_k1 , which corresponds to the coefficient k1 of the first sigmoid function f1(x), is stored.

[0123] Furthermore, the current I is stored in an internal memory of the characteristic curve setting unit 14. ref_k2corresponding to the coefficient k2 of the second sigmoid function f2(x) and the current I ref_k1 stored according to the coefficient k1 of the second sigmoid function f2(x).

[0124] A current I 45 The current flowing from the collector terminal to the emitter terminal of transistor 45 is dependent on the current I. ref_k1 The current I is determined by the variable current source circuit 48, since transistor 45 and transistor 49 form a current mirror. 45 is the sum of the current I 43 , which flows from the collector terminal to the emitter terminal of transistor 43, and the current I 44 , which flows from the collector terminal to the emitter terminal of transistor 44. Therefore, the current I 45 as expressed in the following equation (10). I45=I43+I44

[0125] A voltage difference between the base voltage of transistor 43 and the base voltage of transistor 44 is determined depending on the voltage V. cnt_core determined, and both the current I 43 as well as the current I 44 change depending on the change in V cnt_core .

[0126] While the current I 43 and the current I 44 each with the change of V cnt_core change, the current remains I 45 even when the voltage V changes cnt_core constant.

[0127] When the characteristic curve setting unit 14 then detects the current I ref_k1 When the current changes, it also changes. 43 The current I 43 changes essentially linearly when the absolute value of V Vcnt_core is small. The slope of the linear characteristic curve of the current I 43 changes depending on the current I ref_k1 That is, the slope of the linear characteristic curve of the current I 43changes depending on the coefficient k1.

[0128] More precisely, when the control signal V cnt The current I is applied to input terminal 3, and the characteristic curve setting unit 14 applies it. ref_k1 according to the coefficient k1 of the first sigmoid function f1(x) such that the amplitude P1 of the first amplifier 12 with variable gain is a desired amplitude corresponding to the frequency of the amplification target signal, as in Fig. Figure 2 shows the characteristic curve setting unit 14. The variable current source circuit 48 controls the current I for setting the current. ref_k1 .

[0129] If the current I ref_k1 When set, the amplitude P1 expressed in equation (7) is expressed as in the following equation (11). P1=Grf(Vcnt)=RL⋅g1(Iref_k1)1+exp(−(−RL⋅βIref_k24⋅Vcnt / VT))

[0130] According to the above embodiment 2, the variable gain amplifier 4 is configured such that the first variable gain amplifier 12 further includes the first gain adjustment circuit 47, which adjusts the amplitude of the control signal amplified by the first control signal amplifier 33 on the basis of the coefficient k1 of the first sigmoid function set by the characteristic curve adjustment unit 14, and the second variable gain amplifier 13 further includes the second gain adjustment circuit, which adjusts the amplitude of the control signal amplified by the second control signal amplifier on the basis of the coefficient k1 of the second sigmoid function set by the characteristic curve adjustment unit 14.Consequently, the variable gain amplifier device 4 according to embodiment 2 can achieve a wider band of the target gain signal than the variable gain amplifier device 4 according to embodiment 1. Example 3.

[0131] In embodiment 3, an amplification device 4 with variable amplification is described, in which a characteristic curve setting unit 14 adjusts the coefficients k1 and k2 of the first and second sigmoid functions and, in addition, the coefficient k3 of the first and second sigmoid functions.

[0132] The configuration of a two-input amplifier including the variable-gain amplifier 4 according to embodiment 3 is the same as the configuration of the two-input amplifier including the variable-gain amplifier 4 according to embodiment 1 or the configuration of the two-input amplifier including the variable-gain amplifier 4 according to embodiment 2. Therefore, a circuit diagram showing the two-input amplifier including the variable-gain amplifier 4 according to embodiment 3 is shown in Fig. 1 shown.

[0133] Fig. Figure 8 is a circuit diagram showing the interior of a first amplifier 12 with variable gain of the amplifier device 4 with variable gain according to embodiment 3. It should be noted that in Fig. 8 the same reference symbols as in Fig. 6 and Fig. 7 identical or corresponding parts are designated, so that a detailed description is omitted.

[0134] The interior of a second amplifier 13 with variable gain is the same as the interior of the first amplifier 12 with variable gain, and therefore the circuit diagram showing the interior of the second amplifier 13 with variable gain is omitted.

[0135] The first amplifier 12 with variable gain comprises the resistor 31, the power supply 32, the first control signal amplifier 33, the power supply 40, the first gain target signal amplifier 41, the power supply 46, the first gain adjustment circuit 47 and a first offset adding circuit 50.

[0136] In the case of the second amplifier 13 with variable gain, the in Fig. 8 shown first offset adding circuit 50 a second offset adding circuit.

[0137] The in Fig. The first amplifier 12 with variable gain shown in Figure 8 is created by applying the first offset adding circuit 50 to the circuit shown in Figure 8. Fig. The first amplifier 12 with variable gain shown in Figure 7 is set up. However, this is only an example, and the first amplifier 12 with variable gain can be configured by applying the first offset adding circuit 50 to the first amplifier 12 with variable gain, as shown in Figure 7. Fig. 6 shown, to be set up.

[0138] The first offset adding circuit 50 comprises a variable current source circuit 51, a transistor 52 and a transistor 53.

[0139] The first offset adding circuit 50 adds an offset to a control signal amplified by the first control signal amplifier 33, based on the coefficient k3 set by the characteristic curve adjustment unit 14. The coefficient k3 is a coefficient for adjusting a shift of a curve that specifies the first variable gain characteristic or the first variable gain properties. More precisely, the coefficient k3 is the coefficient for shifting the first variable gain characteristic in the direction of the horizontal axis. Fig. 4.

[0140] The variable current source circuit 51 outputs a current I ref_k3 , which corresponds to the coefficient k3 set by the characteristic curve setting unit 14, to a collector terminal and a base terminal of the transistor 52.

[0141] The collector terminal of transistor 52 is connected to an output side of the variable current source circuit 51, the base terminal of transistor 52 and a base terminal of transistor 53.

[0142] One emitter terminal of transistor 52 is connected to ground.

[0143] The base terminal of transistor 52 is connected to the output side of the variable current source circuit 48, the collector terminal of transistor 52 and the base terminal of transistor 53.

[0144] The base terminal of transistor 53 is connected to the base terminal of transistor 52, the collector terminal of transistor 52 and the output side of the variable current source circuit 51.

[0145] One collector terminal of transistor 53 is connected to the collector terminal of transistor 37, the other end of resistor 36 and the base terminal of transistor 43.

[0146] One emitter terminal of transistor 53 is connected to ground.

[0147] Next, the operation of the two-input amplifier according to embodiment 3 will be described. Since, with the exception of the characteristic curve setting unit 14 and the first offset adding circuit 50, the components are the same as those of the two-input amplifier according to embodiment 2, the functions of the characteristic curve setting unit 14 and the first offset adding circuit 50 will be described in detail below.

[0148] For example, the current I is stored in an internal memory of the characteristic curve setting unit 14. ref_k2 corresponding to the coefficient k2 of the first sigmoid function f1(x), the current I ref_k1 corresponding to the coefficient k1 of the first sigmoid function f1(x) and the current I ref_k3 stored according to the coefficient k3 of the first sigmoid function f1(x).

[0149] Furthermore, the current I is stored in the internal memory of the characteristic curve setting unit 14. ref_k2 corresponding to the coefficient k2 of the second sigmoid function f2(x), the current I ref_k1 corresponding to the coefficient k1 of the second sigmoid function f2(x) and the current I ref_k3 stored according to the coefficient k3 of the second sigmoid function f2(x).

[0150] A current I 53 The current flowing from the collector terminal to the emitter terminal of transistor 53 is dependent on the current I. ref_k3 determined, which is output by the variable current source circuit 51, since transistor 52 and transistor 53 form a current mirror.

[0151] Thus, if the characteristic curve setting unit 14 controls the current I ref_k3 When the current changes, it also changes. 53 If the current I 53 The voltage V changes cnt_core delay.

[0152] If the voltage V cnt_core depending on the change in current I 53 When the amplitude P1 is shifted, it is expressed as in the following equation (12). P1=Grf(Vcnt)=RL⋅g1(Iref_k1)1+exp(−RLVT⋅(−βIref_k24Vcnt−γIref_k3))

[0153] In equation (12) y represents the current mirror ratio between transistor 52 and transistor 53.

[0154] If the control signal V cnt When a current is applied to input terminal 3, the characteristic curve setting unit 14 sets the current I. ref_k3 according to the coefficient k3 of the first sigmoid function f(x) such that, as in Fig. Figure 4 shows the gain of the first amplifier 12 with variable gain according to the frequency of the target signal. The characteristic curve setting unit 14 controls the variable current source circuit 51 to adjust the current I. ref_k3 .

[0155] According to the above embodiment 3, the variable gain amplifier 4 is configured such that the first variable gain amplifier 12 further includes the first offset adding circuit 50, which adds an offset or shift to the control signal amplified by the first control signal amplifier 33 based on the coefficient k3 set by the characteristic curve setting unit 14, and the second variable gain amplifier 13 further includes the second offset adding circuit, which adds an offset to the control signal amplified by the second control signal amplifier based on the coefficient k3 set by the characteristic curve setting unit 14. Consequently, the variable gain amplifier 4 according to embodiment 3 can achieve a wider range of the target gain signal than the variable gain amplifiers 4 according to embodiments 1 and 2. Example 4.

[0156] In embodiment 4, an amplification device 4 with variable amplification is described, in which a characteristic curve setting unit 14 adjusts the coefficients k1, k2 and k3 of the first and second sigmoid functions and additionally the coefficient k4 of the first and second sigmoid functions.

[0157] The configuration of a two-input amplifier including the variable-gain amplifier 4 according to embodiment 4 is the same as the configuration of the two-input amplifier including the variable-gain amplifier 4 according to embodiment 1, the configuration of the two-input amplifier including the variable-gain amplifier 4 according to embodiment 2, or the configuration of the two-input amplifier including the variable-gain amplifier 4 according to embodiment 3. Therefore, a circuit diagram showing the two-input amplifier including the variable-gain amplifier 4 according to embodiment 4 is shown in Fig. 1 shown.

[0158] Fig. Figure 9 is a circuit diagram showing the interior of a first amplifier 12 with variable gain of the amplifier device 4 with variable gain according to embodiment 4. It should be noted that in Fig. 9 the same reference symbols as in Fig. 6, Fig. 7 and Fig. 8 identical or corresponding parts are designated, so that a detailed description can be omitted.

[0159] The interior of a second amplifier 13 with variable gain is the same as the interior of the first amplifier 12 with variable gain, and therefore the circuit diagram showing the interior of the second amplifier 13 with variable gain is omitted.

[0160] The first variable gain amplifier 12 includes the resistor 31, the power supply 32, the first control signal amplifier 33, the power supply 40, the first gain target signal amplifier 41, the power supply 46, the first gain setting circuit 47, the first offset adding circuit 50 and a third offset adding circuit 54.

[0161] In the case of the second amplifier 13 with variable gain, the in Fig. 9 shown third offset adding circuit 54 a fourth offset adding circuit.

[0162] The in Fig. The first amplifier 12 with variable gain shown in Figure 9 is created by applying the third offset adding circuit 54 to the circuit shown in Figure 9. Fig. The first amplifier 12 with variable gain shown in Figure 8 is set up. However, this is only an example, and the first amplifier 12 with variable gain can be configured by adding the third offset adding circuit 54 to the first amplifier 12 with variable gain shown in Figure 8. Fig. 6 is shown, or on the first amplifier 12 with variable gain, which is in Fig. As shown in section 7, it is applied.

[0163] The third offset adding circuit 54 comprises a variable current source circuit 55, a transistor 56 and a transistor 57.

[0164] The third offset adding circuit 54 adds an offset to a signal amplified by the first gain target signal amplifier 41, based on the coefficient k4 set by the characteristic curve setting unit 14. The coefficient k4 is a coefficient for setting the shift of a curve that specifies the first variable gain characteristics. More precisely, the coefficient k4 is the coefficient for shifting the first variable gain characteristics in the direction of the vertical axis. Fig. 5.

[0165] The variable current source circuit 55 outputs a current I ref_k4 , which corresponds to the coefficient k4 set by the characteristic curve setting unit 14, to a collector terminal and a base terminal of the transistor 56.

[0166] The collector terminal of transistor 56 is connected to an output side of the variable current source circuit 55, the base terminal of transistor 56 and a base terminal of transistor 57.

[0167] One emitter terminal of transistor 56 is connected to ground.

[0168] The base terminal of transistor 56 is connected to the output side of the variable current source circuit 55, the collector terminal of transistor 56 and the base terminal of transistor 56.

[0169] The base terminal of transistor 57 is connected to the base terminal of transistor 56, the collector terminal of transistor 56 and the output side of the variable current source circuit 55.

[0170] One collector terminal of transistor 57 is connected to the collector terminal of transistor 43, the other end of resistor 42 and the output terminal V. out tied together.

[0171] One emitter terminal of transistor 57 is connected to ground.

[0172] Next, the operation of the two-input amplifier according to embodiment 4 will be described. Since the components, with the exception of the characteristic curve setting unit 14 and the third offset adding circuit 54, are the same as those of the two-input amplifier according to embodiment 3, the functions of the characteristic curve setting unit 14 and the third offset adding circuit 54 will be described mainly below.

[0173] For example, the current I is stored in the internal memory of the characteristic curve setting unit 14. ref_k2 , which corresponds to the coefficient k2 of the first sigmoid function f1(x), the current I ref_k1 , which corresponds to the coefficient k1 of the first sigmoid function f1(x), the current I ref_k3 , which corresponds to the coefficient k3 of the first sigmoid function f1(x), and the current I ref_k4, which corresponds to the coefficient k k4 The first sigmoid function f1(x) is stored.

[0174] Furthermore, the current I is stored in an internal memory of the characteristic curve setting unit 14. ref_k2 , which corresponds to the coefficient k2 of the second sigmoid function f2(x), the current I ref_k1 , which corresponds to the coefficient k1 of the second sigmoid function f2(x), the current I ref_k3 , which corresponds to the coefficient k3 of the second sigmoid function f2(x), and the current I ref_k4 , which corresponds to the coefficient k4 of the second sigmoid function, is stored.

[0175] A current I 57 The current flowing from the collector terminal to the emitter terminal of transistor 57 is dependent on the current I. ref_k4 determined, which is output by the variable current source circuit 55, since transistor 56 and transistor 57 form a current mirror.

[0176] Therefore, if the characteristic curve setting unit 14 detects the current I ref_k4 When the current changes, it also changes. 57 If the current I 57 The change will affect the output terminal V. out Output voltage shifted.

[0177] If the voltage V cnt_core depending on the change in current I 57 When the amplitude P1 is shifted, it is expressed as in the following equation (13). P1=Grf(Vcnt)=RL⋅g1(Iref_k1)1+exp(−RLVT⋅(−βIref_k24Vcnt−γIref_k3))+g11(Iref_k4)

[0178] In equation (13) g 11 for the amplification of the third offset adding circuit 54.

[0179] If the control signal V cnt When a current is applied to input terminal 3, the characteristic curve setting unit 14 sets the current I. ref_k4 according to the coefficient k4 of the first sigmoid function f(x) such that, as in Fig.Figure 5 shows the gain of the first amplifier 12 with variable gain according to the frequency of the target signal. The characteristic curve adjustment unit 14 controls the variable current source circuit 55 to adjust the current I. ref_k4 .

[0180] According to the above embodiment 4, the variable gain amplifier 4 is configured such that the first variable gain amplifier 12 also includes the third offset adding circuit 54, which adds an offset based on the coefficient k4, set by the characteristic curve setting unit 14, to the one signal that is amplified by the first gain target signal amplifier 41, and the second variable gain amplifier 13 also includes the fourth offset adding circuit, which adds an offset based on the coefficient k4, set by the characteristic curve setting unit 14, to the other signal that is amplified by the second gain target signal amplifier.Consequently, the variable gain amplifier device 4 according to embodiment 4 can achieve a wider band of the target gain signal than the variable gain amplifier devices 4 according to embodiments 1 and 3.

[0181] It should be noted that the present disclosure permits any combination of the embodiments, any modifications of the components in the embodiments, or the omission of components in the embodiments. COMMERCIAL APPLICABILITY

[0182] The present disclosure is suitable for a variable gain amplifier and a dual-input amplifier. REFERENCE MARK LIST

[0183] 1, 2, 3: Input terminal, 4: Variable gain amplifier, 11: Splitter, 12: First variable gain amplifier, 13: Second variable gain amplifier, 14: Characteristic curve adjustment unit, 20: Dual input amplifier, 21: First gain element, 22: Second gain element, 23: Output terminal, 31: Resistor, 32: Power supply, 33: First control signal amplifier, 34: Variable current source circuit, 35: Transistor, 36: Resistor, 37, 38, 39: Transistor, 40: Power supply, 41: First gain target signal amplifier, 42: Resistor, 43, 44, 45: Transistor, 46: Power supply, 47: First gain adjustment circuit, 48: Variable current source circuit, 49: Transistor, 50: First offset adding circuit, 51: Variable current source circuit 52, 53: Transistor, 54: Third offset adding circuit, 55: Variable current source circuit, 56: Transistor, 57: Transistor QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP H2-100406 A

[0004]

Claims

[1] Amplification device with variable gain comprising: a splitter for splitting an amplification target signal into two signals and for outputting one signal and another signal contained in the two signals; a first variable-gain amplifier to amplify the one signal in accordance with first variable-gain characteristics and to output the amplified signal to a first amplifying element, wherein the first variable-gain amplifier has the first variable-gain characteristics, the gain of which is expressed by a first sigmoid function according to a control signal indicating a magnitude of an envelope of the amplification target signal; a second variable-gain amplifier to amplify the other signal according to second variable-gain characteristics and to output the other amplified signal to a second amplifying element, wherein the second variable-gain amplifier has the second variable-gain characteristics, the gain of which is expressed by a second sigmoid function according to the control signal; and A characteristic curve setting unit to set one or more gains under a gain of the first sigmoid function and a gain of the second sigmoid function depending on a frequency of the gain target signal. [2] Amplification device with variable gain according to claim 1, wherein the characteristic curve setting unit sets the gain of the first sigmoid function and the gain of the second sigmoid function as a function of the frequency of the gain target signal. [3] Amplification device with variable amplification according to claim 2, wherein the first sigmoid function is f1(x) and the second sigmoid function is f2(x), and The characteristic curve setting unit adjusts the gain of the first sigmoid function f1(x) by setting a coefficient k2 of f1(x) and the gain of the second sigmoid function f2(x) by setting a coefficient k2 of f2(x). f1(x)=k11+exp(−(k2x−k3))+k4 f2(x)=k11+exp(−(k2x−k3))+1−k4 where x represents the control signal and k1, k2, k3 and k4 each represent a coefficient of the first sigmoid function and the second sigmoid function. [4] Amplification device with variable gain according to claim 3, wherein the characteristic curve setting unit sets each of the coefficient k2 of the first sigmoid function and the coefficient k2 of the second sigmoid function as a function of the frequency of the gain target signal, and additionally sets each of a coefficient k1, a coefficient k3 and a coefficient k4 of the first sigmoid function and sets each of a coefficient k1, a coefficient k3 and a coefficient k4 of the second sigmoid function. [5] Amplification device with variable amplification according to claim 4, wherein the first amplifier with variable gain includes a first control signal amplifier for amplifying an externally supplied control signal based on the coefficient k2 of the first sigmoid function, which is set by the characteristic curve setting unit, and a first gain target signal amplifier to amplify the signal output by the splitter in accordance with the control signal amplified by the first control signal amplifier and to output the amplified signal to the first gain amplifier, and the second amplifier with variable gain includes a second control signal amplifier for amplifying an externally supplied control signal based on the coefficient k2 of the second sigmoid function, which is set by the characteristic curve setting unit, and a second gain target signal amplifier to amplify the other signal output by the splitter in accordance with the control signal amplified by the second control signal amplifier and to output the other amplified signal to the second gain element. [6] Amplification device with variable amplification according to claim 5, wherein the first variable-gain amplifier further includes a first gain-adjusting circuit to adjust the amplitude of the control signal amplified by the first control signal amplifier based on the coefficient k1 of the first sigmoid function, which is set by the characteristic curve adjustment unit, and The second variable gain amplifier also includes a second gain adjustment circuit to adjust the amplitude of the control signal amplified by the second control signal amplifier based on the coefficient k1 of the second sigmoid function, which is set by the characteristic curve adjustment unit. [7] Amplification device with variable amplification according to claim 5, wherein the first variable-gain amplifier further includes a first offset adding circuit to add an offset to the control signal amplified by the first control signal amplifier, based on the coefficient k3 of the first sigmoid function, which is set by the characteristic curve setting unit, and The second variable gain amplifier also includes a second offset adding circuit to add an offset to the control signal amplified by the second control signal amplifier, based on the coefficient k3 of the second sigmoid function, which is set by the characteristic curve setting unit. [8] Amplification device with variable amplification according to claim 5, wherein The first variable-gain amplifier further includes a third offset-adder circuit to add an offset to the single signal amplified by the first gain-target signal amplifier based on the coefficient k4 of the first sigmoid function, which is set by the characteristic curve setting unit, and The second variable gain amplifier also includes a fourth offset adding circuit to add an offset to the other signal that is amplified by the second gain target signal amplifier based on the coefficient k4 of the second sigmoid function, which is set by the characteristic curve setting unit. [9] Amplifier device with two inputs comprising: a splitter for splitting an amplification target signal into two signals and for outputting one signal and another signal contained in the two signals; a first variable-gain amplifier to amplify the one signal in accordance with first variable-gain characteristics, wherein the first variable-gain amplifier has the first variable-gain characteristics, the gain of which is expressed by a first sigmoid function according to a control signal indicating a magnitude of an envelope of the target amplification signal; a second variable-gain amplifier for amplifying the other signal in accordance with second variable-gain characteristics, wherein the second variable-gain amplifier has the second variable-gain characteristics, the gain of which is expressed by a second sigmoid function in accordance with the control signal; a characteristic curve setting unit for setting one or more gains based on a gain of the first sigmoid function and a gain of the second sigmoid function as a function of a frequency of the target gain signal; and an amplifier with two inputs for outputting a synthesis signal from a signal amplified by a first amplification element and another signal amplified by a second amplification element, wherein the amplifier with two inputs comprises the first amplification element for amplifying the one signal amplified by the first amplifier with variable gain and the second amplification element for amplifying the other signal amplified by the second amplifier with variable gain.

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