Amplification device

Abstract

To provide an amplification device capable of meeting various requirements in a signal transmission by future optical communication.SOLUTION: An amplification device 1 includes a first amplification part 10, a second amplification part 20, an amplitude detection part 30, and a control part 40. In the first amplification part 10, any gain may be set from among a plurality of discrete gains. The first amplification part 10 converts an input current signal into a voltage signal based on the set gain, and outputs the converted voltage signal to the second amplification part 20. In the second amplification part 20, any gain may be set from a continuous gain variable range. The second amplification part 20 amplifies the voltage signal output from the first amplification part 10 based on the set gain, and outputs the amplified voltage signal. The control part 40 controls the gains of the first amplification part 10 and the second amplification part 20 so that the amplitude detected by the amplitude detector 30 becomes constant.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an amplification device.

Background Art

[0002] Patent Documents 1 to 3 disclose inventions of devices that convert a current signal (for example, a current signal output from a photodiode which is a light receiving element) into a voltage signal, amplify the voltage signal, and output it. The amplification devices described in these documents include a first amplification unit that converts a current signal into a voltage signal and outputs the voltage signal, and a second amplification unit that amplifies and outputs the voltage signal output from the first amplification unit, and controls so that the amplitude of the voltage signal output from the second amplification unit becomes constant. However, including the devices described in these documents, conventional amplification devices are difficult to use, for example, in a computer network system that is expected to become popular in the future. Hereinafter, this will be described by taking the server system of a data center as an example.

[0003] The current server system of a data center includes a plurality of racks, and each rack includes a plurality of types of resources such as a CPU, a GPU, and a memory. Data transmission and reception are performed both within each rack and between different racks. Since the data transmission and reception within each rack is short-distance, it can be connected by PCIe (peripheral component interconnect express) that enables communication with low latency. However, since the data transmission and reception between different racks has a transmission distance of up to about 30 m, it is connected by Ethernet (registered trademark) but has a large latency. In this configuration, when the processing capacity of a certain rack reaches its limit, even if an attempt is made to distribute the processing to another rack with a surplus of processing capacity, it is difficult to improve the processing capacity because of the large latency of data transmission and reception between these two racks.

[0004] In a server system expected to become widespread in the future, each rack becomes a resource pool that aggregates any one type of resource among resources such as CPUs, GPUs, and memories, and the racks are connected with low latency. Since all resource pools can be connected to each other with low latency, there is no resource with a surplus of processing power, and it becomes possible to maximize the processing power. This new server system is called resource-dispersed computing, etc. For further improvement of processing power, high speed and low power consumption are also required.

[0005] PCIe 6.0 has been released as a new standard to meet various requirements of server systems. In this standard, while achieving high speed, it aims to achieve low latency by adopting a lightweight FEC (3-way interleaved single symbol correction) as forward error correction (FEC). Also, in this standard, it is required to make the SER (Symbol Error Rate) before FEC smaller than before.

[0006] Also, in conventional PCIe transmission, data transmission has been performed using copper wiring, but mid-distance low-latency transmission of about 30 m, which is necessary to realize resource-dispersed computing, is difficult. Therefore, it has been proposed to realize mid-distance transmission by performing data transmission by optical communication instead of copper wiring. However, optical communication has problems such as high power consumption and large latency due to reasons such as the use of DSP. Note that the DSP is used as an equalizer on the transmission side, and the DSP is used as a distortion correction circuit on the reception side.

[0007] If we decide not to use a DSP in order to achieve low power consumption and low latency, it becomes important to suppress the deterioration of the eye of the transmission signal. On the other hand, in PCIe6.0, it is required to make the SER before FEC smaller than before. From these facts, it is required to suppress the noise component of the eye of the optical communication signal, and furthermore, in order to do so, it is required to reduce the noise of the optical communication receiving amplifier circuit due to the necessity of improving the signal-to-noise ratio on the optical signal receiving side of the optical communication.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] As described above by taking the server system of the data center as an example, in view of the future development direction of signal transmission, it is important that various requirements are satisfied in signal transmission by optical communication. However, the amplification devices described in Patent Documents 1 to 3 are difficult to meet these requirements.

[0010] In the amplification device described in Patent Document 1, the gain of the first amplification unit is fixed, and the gain of the second amplification unit is controlled so that the amplitude of the voltage signal output from the second amplification unit becomes constant. In the first amplification unit with a fixed gain, it is difficult to simultaneously meet the requirements of both low noise and a wide dynamic range.

[0011] That is, in the first amplification unit where the gain is fixed, it is necessary to set a high gain to meet the requirement of low noise. However, in that case, if the amplitude of the input current signal is large, the output voltage signal will be distorted. To prevent the output voltage signal from being distorted even when the amplitude of the input current signal is large, it is necessary to set a low gain. However, in that case, the noise characteristics will deteriorate.

[0012] In future optical communications, in order to meet the strong requirement of low power consumption, it is expected that a vertical cavity surface emitting laser (VCSEL), which is advantageous for low power consumption as a light emitting element on the transmission side, will be used. However, the characteristic variations of VCSELs are large. Therefore, it is required that the input dynamic range of the first amplification unit be wide. Also, as described above, it is required to reduce the SER before FEC. However, in the first amplification unit with a fixed gain, it is difficult to simultaneously meet the requirements of both low noise and a wide dynamic range.

[0013] In the amplification device described in Patent Document 2, each of the first amplification unit and the second amplification unit can be set to any gain within the continuous gain variable range, and the gains of the first amplification unit and the second amplification unit are controlled so that the amplitude of the voltage signal output from the second amplification unit becomes constant. With this configuration, it is possible to simultaneously meet the requirements of both low noise and a wide dynamic range.

[0014] However, when the input and output current and voltage signals are PAM4 signals, it is required that the flatness of the frequency characteristics be good over a wide input current range. However, if the gain of the first amplification unit can be arbitrarily set within the continuous gain variable range, it is difficult to meet this requirement. That is, when the first amplification unit that converts a current signal into a voltage signal is a feedback type trans-impedance amplifier (TIA), since the input impedance is proportional to the gain (feedback resistance value), the influence on the main pole of the frequency characteristics is large. Also, when the first amplification unit is a base-grounded TIA, the bias current flowing through the base-grounded amplifier changes, and the operating point (collector-emitter voltage) of the transistor also changes. Therefore, due to the change in the ft of the transistor, the influence on the main pole of the frequency characteristics is large. Therefore, it is difficult to keep the frequency characteristics flat while performing continuous gain control.

[0015] In the amplification device described in Patent Document 3, each of the first amplification unit and the second amplification unit can be set to any one of a plurality of discrete gains, and the gains of the first amplification unit and the second amplification unit are controlled so that the amplitude of the voltage signal output from the second amplification unit becomes constant. In this configuration, it is possible to adjust the flattening of the frequency characteristics for each setting of the gain in the first amplification unit.

[0016] However, in order to realize a wide dynamic range, it is necessary to enable a large number of gain settings in each of the first amplification unit and the second amplification unit. Therefore, the circuit scale of the control unit for controlling the gains of the first amplification unit and the second amplification unit is large. In the amplification device described in Patent Document 3, the first amplification unit is set to any one of more than 2000 gains according to the amplitude of the output voltage signal of the second amplification unit. Also, the second amplification unit is set to any one of a plurality of gains according to the amplitude of the output voltage signal of the second amplification unit and the gain of the first amplification unit. Thus, the circuit scale of the control unit for controlling the gains of the first amplification unit and the second amplification unit is large.

[0017] In addition, since the amplification device is also required to output a large amplitude in order to support PCIe 6.0, it is difficult to adopt a state-of-the-art CMOS process that has constraints in terms of power supply voltage, and it is desirable to adopt a BiCMOS process. However, compared with the state-of-the-art CMOS process, the BiCMOS process has a larger logic scale, and it is difficult to reduce the circuit area of the control unit. Thus, in the amplification device described in Patent Document 3, the circuit scale of the control unit for controlling the gain is large and the circuit area is also large, which is a factor contributing to cost increase. Since the optical cable length required for future optical communication will be a short medium distance of about 30 m, which is shorter than existing optical cables, the cost requirement will become stronger than ever.

[0018] As described above, the amplification devices described in Patent Documents 1 to 3 cannot meet the various requirements in signal transmission by future optical communication.

[0019] The present invention has been made to solve the above problems, and an object thereof is to provide an amplification device that can meet the various requirements in signal transmission by future optical communication.

Means for Solving the Problems

[0020] A first aspect of the amplification device of the present invention includes: (1) a first amplification unit that sets any one of a plurality of discrete gains, converts an input current signal into a voltage signal based on the set gain, and outputs the converted voltage signal; (2) a second amplification unit that sets any one of a continuously variable gain range, amplifies the voltage signal output from the first amplification unit based on the set gain, and outputs the amplified voltage signal; (3) an amplitude detection unit that detects the amplitude of the voltage signal output from the second amplification unit; and (4) a control unit that controls the gains of the first amplification unit and the second amplification unit so that the amplitude detected by the amplitude detection unit becomes constant.

[0021] In the second aspect of the amplification device of the present invention, in addition to the first aspect, the control unit controls the gain of the second amplification unit so that the amplitude detected by the amplitude detection unit becomes constant, and when the gain of the second amplification unit deviates from the range of not less than the first threshold value and not more than the second threshold value within the continuously variable gain range, the control unit changes the gain of the first amplification unit.

[0022] In the third aspect of the amplification device of the present invention, in addition to the second aspect, after a certain period has elapsed since the control unit changes the gain of the first amplification unit, when the gain of the second amplification unit deviates from the range of not less than the first threshold value and not more than the second threshold value, the control unit changes the gain of the first amplification unit.

[0023] In the fourth aspect of the amplification device of the present invention, in addition to the second aspect or the third aspect, when the gain of the second amplification unit is less than the first threshold value, the control unit changes the gain of the first amplification unit to a gain that is smaller by one setting, and when the gain of the second amplification unit exceeds the second threshold value, the control unit changes the gain of the first amplification unit to a gain that is larger by one setting. Alternatively, when the gain of the second amplification unit exceeds the first threshold value, the control unit may change the gain of the first amplification unit to a gain that is smaller by one setting, and when the gain of the second amplification unit is less than the second threshold value, the control unit may change the gain of the first amplification unit to a gain that is larger by one setting.

[0024] In the fifth aspect of the amplification device of the present invention, in addition to the second aspect or the third aspect, when the gain of the second amplification unit is less than the first threshold value, the control unit changes the gain of the first amplification unit to a gain that is smaller by one setting, and when the gain of the second amplification unit exceeds the second threshold value, the control unit changes the gain of the first amplification unit to the maximum gain. Alternatively, when the gain of the second amplification unit exceeds the first threshold value, the control unit may change the gain of the first amplification unit to a gain that is smaller by one setting, and when the gain of the second amplification unit is less than the second threshold value, the control unit may change the gain of the first amplification unit to the maximum gain.

[0025] In the sixth aspect of the amplification device of the present invention, in addition to any one of the first to fifth aspects, the control unit changes the impedance value or current value of the element included in the first amplification unit according to the gain of the first amplification unit.

Advantages of the Invention

[0026] According to the present invention, an amplification device capable of meeting various requirements in future signal transmission by optical communication can be provided.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0028] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are given to the same elements, and redundant descriptions are omitted. The present invention is not limited to these examples, but is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0029] FIG. 1 is a diagram showing the configuration of the amplification device 1. The amplification device 1 is a device that converts an input current signal into a voltage signal and outputs the voltage signal, and includes a first amplification unit 10, a second amplification unit 20, an amplitude detection unit 30, and a control unit 40. The current signal input to the amplification device 1 is, for example, output from a light receiving element. Further, it is preferable that this light receiving element is a photodiode.

[0030] The first amplification unit 10 can have any one of a plurality of discrete gains set. The first amplification unit 10 converts the input current signal into a voltage signal based on the set gain, and outputs the converted voltage signal to the second amplification unit 20.

[0031] The second amplification unit 20 can have any one of a continuous gain variable range set. The second amplification unit 20 amplifies the voltage signal output from the first amplification unit 10 based on the set gain, and outputs the amplified voltage signal.

[0032] Let the gain of the first amplification unit 10 be G1 [Ω], and the gain of the second amplification unit 20 be G2 [times]. The overall gain of the amplification device 1 is G1G2 [Ω]. Let the amplitude of the current signal input to the first amplification unit 10 be A0 [A]. Let the amplitude of the voltage signal output from the first amplification unit 10 and input to the second amplification unit 20 be V1 [V]. Let the amplitude of the voltage signal output from the second amplification unit 20 be V2 [V]. There is a relationship represented by the following equation among these parameters. V1 = A0G1 V2 = V1G2 = A0G1G2

[0033] The amplitude detection unit 30 detects the amplitude V2 of the voltage signal output from the second amplification unit 20. The control unit 40 controls the gain G1 of the first amplification unit 10 and the gain G2 of the second amplification unit 20 so that the amplitude V2 detected by the amplitude detection unit 30 becomes constant.

[0034] The control unit 40 supplies a first gain control signal for setting the gain G1 of the first amplification unit 10 to the first amplification unit 10. The first amplification unit 10 sets one of a plurality of discrete gains based on the first gain control signal. The first gain control signal may be a digital signal having a number of bits corresponding to the number of settable gains of the first amplification unit 10.

[0035] The control unit 40 supplies a second gain control signal for setting the gain G2 of the second amplification unit 20 to the second amplification unit 20. The second amplification unit 20 sets one of the continuous gain variable ranges based on the second gain control signal. The second gain control signal may be a voltage signal (analog signal) that can take a value corresponding to a value within the continuous gain variable range of the second amplification unit 20.

[0036] The amplification device 1 having such a configuration can achieve both low noise and a wide dynamic range because one of a plurality of discrete gains is set in the first amplification unit 10, and it is also possible to adjust the flattening of the frequency characteristics for each gain setting. Also, while one of a plurality of discrete gains is set in the first amplification unit 10, one of the continuous gain variable ranges is set in the second amplification unit 20, so it is possible to reduce the circuit scale of the control unit 40 for controlling the gains of the first amplification unit 10 and the second amplification unit 20 respectively, and this contributes to cost reduction.

[0037] Figures 2 to 5 are diagrams for explaining operation examples (control examples of the control unit 40) of the amplification device 1. In any of the operation examples described below, the amplification device 1 performs a continuous AGC operation and a gain G1 change operation under the control of the control unit 40.

[0038] In the first operation example shown in FIG. 2, the control unit 40 feedback-controls the gain G2 of the second amplifier unit 20 so that the amplitude V2 detected by the amplitude detection unit 30 becomes constant in a state where the gain G1 of the first amplifier unit 10 is set to a certain set value (continuous AGC operation). Further, when the gain G2 of the second amplifier unit 20 deviates from the set range of equal to or higher than the first threshold value and equal to or lower than the second threshold value within the continuous gain variable range during the continuous AGC operation (that is, when the value of the second gain control signal deviates from the set range), the control unit 40 changes the gain G1 of the first amplifier unit 10 (gain G1 change operation). The change in the gain G1 of the first amplifier unit 10 during the gain G1 change operation is not limited to the change to a gain that is one setting larger or one setting smaller than the previous gain. After the gain G1 change operation, the control unit 40 performs the continuous AGC operation in a state where the gain G1 of the first amplifier unit 10 is set to a new set value.

[0039] Whether or not the gain G2 of the second amplifier unit 20 has deviated from the set range of equal to or higher than the first threshold value and equal to or lower than the second threshold value within the continuous gain variable range during the continuous AGC operation can be determined by monitoring the value of the second gain control signal for setting the gain G2 and determining whether or not this value of the second gain control signal has deviated from the set range of equal to or higher than the first voltage threshold value and equal to or lower than the second voltage threshold value. Note that the relationship between the value of the second gain control signal and the gain G2 may be either a positive correlation or a negative correlation, and one of the first voltage threshold value and the second voltage threshold value of the second gain control signal is for setting the gain G2 to the first threshold value, and the other is for setting the gain G2 to the second threshold value.

[0040] In the second operation example shown in FIG. 3, when the gain G2 of the second amplifier unit 20 deviates from the set range during the continuous AGC operation after a certain period has elapsed since the control unit 40 changed the gain G1 of the first amplifier unit 10, the control unit 40 performs the gain G1 change operation. Here, the certain period is the period required for the amplitude V2 of the output voltage signal to stabilize after the gain G1 of the first amplifier unit 10 is changed to a new set value. In this second operation example, the interference between the continuous AGC operation and the gain G1 change operation is suppressed, and a more stable operation becomes possible.

[0041] In the third operation example shown in FIG. 4, in the gain G1 change operation, when the gain G2 of the second amplifier 20 falls below the first threshold value during the continuous AGC operation, the control unit 40 changes the gain G1 of the first amplifier 10 to a gain that is one setting smaller, and when the gain G2 of the second amplifier 20 exceeds the second threshold value during the continuous AGC operation, the control unit 40 changes the gain G1 of the first amplifier 10 to a gain that is one setting larger. Alternatively, the control unit 40 may change the gain G1 of the first amplifier 10 to a gain that is one setting smaller when the gain G2 of the second amplifier 20 exceeds the first threshold value, and change the gain G1 of the first amplifier 10 to a gain that is one setting larger when the gain G2 of the second amplifier 20 falls below the second threshold value.

[0042] In the fourth operation example shown in FIG. 5, in the gain G1 change operation, when the gain G2 of the second amplifier 20 falls below the first threshold value during the continuous AGC operation, the control unit 40 changes the gain G1 of the first amplifier 10 to a gain that is one setting smaller, and when the gain G2 of the second amplifier 20 exceeds the second threshold value during the continuous AGC operation, the control unit 40 changes the gain G1 of the first amplifier 10 to the maximum gain. Alternatively, the control unit 40 may change the gain G1 of the first amplifier 10 to a gain that is one setting smaller when the gain G2 of the second amplifier 20 exceeds the first threshold value, and change the gain G1 of the first amplifier 10 to the maximum gain when the gain G2 of the second amplifier 20 falls below the second threshold value.

[0043] Between the third operation example (Fig. 4) and the fourth operation example (Fig. 5), the content of the gain G1 change operation when the gain G2 of the second amplifier section 20 exceeds the second threshold value during continuous AGC operation is different. In the third operation example, during the gain G1 change operation, there are cases where the gain G1 of the first amplifier section 10 is changed to a gain smaller by one setting and cases where the gain G1 of the first amplifier section 10 is changed to a gain larger by one setting. From this, in the third operation example, an up-down counter is required as a counter for holding the set value of the gain G1 of the first amplifier section 10. On the other hand, in the fourth operation example, during the gain G1 change operation, there are cases where the gain G1 of the first amplifier section 10 is changed to a gain smaller by one setting, while when the gain G1 of the first amplifier section 10 is changed to a larger gain, it is changed to the maximum gain. From this, in the fourth operation example, an up counter or a down counter is sufficient as a counter for holding the set value of the gain G1 of the first amplifier section 10. Therefore, compared with the third operation example, in the fourth operation example, the scale of the logic circuit for setting the gain G1 of the first amplifier section 10 can be reduced.

[0044] Also, when changing the gain G1 of the first amplifier unit 10 to a large gain as in the fourth operation example, it is preferable to change it to the maximum gain. Conversely, when changing the gain G1 of the first amplifier unit 10 to a small gain, it is not preferable to change it to the minimum gain. The reasons are as follows. In PCIe, when signal communication stops in the low power state, it enters the Electrical Idle state and becomes a no-signal input state. At this time, since the gain is maximum in the initial state of the continuous AGC operation, it is preferable that the gain G1 of the first amplifier unit 10 is also set to the maximum in the initial state. When a current signal is input, the gain G1 of the first amplifier unit 10 may be gradually decreased from the maximum setting. Also, when the state becomes one where no current signal is input, since there is no need to gradually increase the gain G1 of the first amplifier unit 10, the gain G1 of the first amplifier unit 10 may be set to the maximum gain all at once. Also, when the gain G1 of the first amplifier unit 10 is small, the noise characteristics are poor. Therefore, if a current signal with a small amplitude is input in that state, there is a risk that a waveform that cannot be distinguished as either a signal or noise will be output at the output of the first amplifier unit 10. For these reasons, it is not preferable to change the gain G1 of the first amplifier unit 10 to the minimum gain all at once when changing it to a small gain.

[0045] Next, an example of setting the gain G1 of the first amplifier unit 10 and the gain G2 of the second amplifier unit 20 by the control unit 40 will be described. Here, it is assumed that the control unit 40 controls the gain G1 of the first amplifier unit 10 and the gain G2 of the second amplifier unit 20 so that the amplitude V2 of the output voltage signal is constant at 1V.

[0046] Let the three gains to be discretely set in the first amplifier unit 10 be G 1,1 ~G 1,3 Let the gain of the second amplifier unit 20 when the gain of the first amplifier unit 10 is G 1,1 be G 2,1 Let the gain of the second amplifier unit 20 when the gain of the first amplifier unit 10 is G 1,2 be G 2,2 Let the gain of the second amplifier unit 20 when the gain of the first amplifier unit 10 is G 1,3 be G 2,3 Let the gain of the second amplifier unit 20 be G 2,1 ~G2,3 Each of them changes continuously according to the change in the amplitude A0 of the input current signal.

[0047] FIG. 6 is a diagram showing the relationship between the overall gain G1G2 of the amplification device 1 and the amplitude A0 of the input current signal. The overall gain G1G2 of the amplification device 1 is in an inverse proportional relationship with the amplitude A0 of the input current signal.

[0048] FIG. 7 1,1 = 1000Ω, G 1,2 = 500Ω, G 1,3 = 250Ω, is a diagram showing a setting example of the gain G1 of the first amplification unit 10 and the gain G2 of the second amplification unit 20. FIG. 7(a) is a diagram showing the relationship between the gain G1 of the first amplification unit 10 and the amplitude A0 of the input current signal. FIG. 7(b) is a diagram showing the relationship between the gain G2 of the second amplification unit 20 and the amplitude A0 of the input current signal. In this setting example, since G 1,1 / G 1,2 = G 1,2 / G 1,3 = 2, accordingly, at each value of the amplitude A0 of the input current signal, G 2,2 / G 2,1 = G 2,3 / G 2,2 = 2 is set.

[0049] FIG. 8 1,1 = 1000Ω, G 1,2 = 400Ω, G 1,3 = 200Ω, is a diagram showing a setting example of the gain G1 of the first amplification unit 10 and the gain G2 of the second amplification unit 20. FIG. 8(a) is a diagram showing the relationship between the gain G1 of the first amplification unit 10 and the amplitude A0 of the input current signal. FIG. 8(b) is a diagram showing the relationship between the gain G2 of the second amplification unit 20 and the amplitude A0 of the input current signal. In this setting example, since G 1,1 / G 1,2 = 2.5, G 1,2 / G 1,3 = 2, accordingly, at each value of the amplitude A0 of the input current signal, G 2,2 / G 2,1 = 2.5, G 2,3 / G 2,2Let it be 2. Also, assuming that the amplitude A0 of the input current signal is 200 μA to 2000 μA, in the range of 200 μA ≤ A0 ≤ 500 μA, G1 = G 1,1 is set to 1000 Ω, and in the range of 500 μA ≤ A0 ≤ 1000 μA, G1 = G 1,2 is set to 400 Ω, and in the range of 1000 μA ≤ A0 ≤ 2000 μA, G1 = G 1,3 When it is set to 200 Ω, the gain G2 of the second amplifier section 20 may be variable in the range of 2 to 5 times.

[0050] As in the setting examples shown in FIGS. 7 and 8, even if the number of adjustable gains G1 of the first amplifier section 10 is as small as 3, the amplitude V2 of the output voltage signal can be controlled to be constant over the entire wide range of the amplitude A0 of the input current signal.

[0051] Next, the configuration of the first amplifier section 10 will be described. FIG. 9 is a diagram showing a schematic configuration of the first amplifier section 10. The first amplifier section 10 inputs the first gain control signal output from the control section 40, is set to any one of a plurality of discrete gains based on this first gain control signal, and has its frequency characteristics adjusted based on this first gain control signal. The adjustment of the frequency characteristics of the first amplifier section 10 is performed by changing the impedance value or current value of an element (resistor, capacitive element, or inductor) included in the first amplifier section 10 according to the gain of the first amplifier section 10.

[0052] FIG. 10 is a diagram showing an example of the circuit configuration of the first amplifier section 10. The first amplifier section 10 shown in this figure can be set to any one of three gains, and includes an NPN transistor 101, an NPN transistor 102, resistors 111 to 113, switches 121 to 123, capacitive elements 131 to 133, resistors 141 to 143, switches 151 to 153, current sources 161 to 163, and switches 171 to 173.

[0053] The collector of the NPN transistor 101 is connected to the node N1. The emitter of the NPN transistor 101 is connected to the low-potential VEE supply terminal. The base of the NPN transistor 101 is connected to an input terminal for inputting a current signal.

[0054] The collector of the NPN transistor 102 is connected to the high-potential VCC supply terminal. The emitter of the NPN transistor 102 is connected to the node N2. The base of the NPN transistor 102 is connected to the node N1 and is also connected to an output terminal for outputting a voltage signal to the second amplifier section 20.

[0055] The resistor 111 and the switch 121 are connected in series with each other and are provided between the VCC supply terminal and the node N1. The resistor 112 and the switch 122 are connected in series with each other and are provided between the VCC supply terminal and the node N1. The resistor 113 and the switch 123 are connected in series with each other and are provided between the VCC supply terminal and the node N1. The resistors 111 to 113 are provided in parallel with each other between the VCC supply terminal and the node N1 and constitute a variable resistor. The resistance value between the VCC supply terminal and the node N1 is set by the on / off states of the switches 121 to 123 respectively.

[0056] The capacitor element 131 and the resistor 141 are connected in parallel with each other, and these are connected in series with the switch 151. The capacitor element 131, the resistor 141, and the switch 151 are provided between the base of the NPN transistor 101 and the node N2.

[0057] The capacitor element 132 and the resistor 142 are connected in parallel with each other, and these are connected in series with the switch 152. The capacitor element 132, the resistor 142, and the switch 152 are provided between the base of the NPN transistor 101 and the node N2.

[0058] The capacitor element 133 and the resistor 143 are connected in parallel with each other, and these and the switch 153 are connected in series with each other. The capacitor element 133, the resistor 143, and the switch 153 are provided between the base of the NPN transistor 101 and the node N2.

[0059] The capacitor elements 131 to 133 and the resistors 141 to 143 are provided in parallel with each other between the base of the NPN transistor 101 and the node N2. The capacitor elements 131 to 133 constitute capacitor elements with variable capacitance values. The resistors 141 to 143 constitute resistors with variable resistance values. The impedance (capacitance value, resistance value) between the base of the NPN transistor 101 and the node N2 is set by the on / off of each of the switches 151 to 153.

[0060] The current source 161 and the switch 171 are connected in series with each other and are provided between the node N2 and the VEE supply terminal. The current source 162 and the switch 172 are connected in series with each other and are provided between the node N2 and the VEE supply terminal. The current source 163 and the switch 173 are connected in series with each other and are provided between the node N2 and the VEE supply terminal. The current sources 161 to 163 are provided in parallel with each other between the node N2 and the VEE supply terminal, and constitute current sources with variable current values flowing from the node N2 to the VEE supply terminal. The current value is set by the on / off of each of the switches 171 to 173.

[0061] Assume that the first gain control signal given from the control unit 40 to the first amplifier unit 10 is a 3-bit digital signal [C3, C2, C1]. Depending on the gain G1 to be set in the first amplifier unit 10, any one of C3, C2, and C1 becomes high level and the other two become low level.

[0062] The on / off of the switches 121, 151, and 171 is set according to the level of C1. The on / off states of switches 122, 152, and 172 are set according to the level of C2. The on / off states of switches 123, 153, and 173 are set according to the level of C3.

[0063] When C1 is at a high level, switches 121, 151, and 171 are in the on state, and the other switches are in the off state. At this time, the gain of the first amplifier section 10 is according to the resistance value of resistor 141. Also, the frequency characteristics of the first amplifier section 10 are according to the resistance value of resistor 111, the capacitance value of capacitor element 131, and the current value of current source 161.

[0064] When C2 is at a high level, switches 122, 152, and 172 are in the on state, and the other switches are in the off state. At this time, the gain of the first amplifier section 10 is according to the resistance value of resistor 142. Also, the frequency characteristics of the first amplifier section 10 are according to the resistance value of resistor 112, the capacitance value of capacitor element 132, and the current value of current source 162.

[0065] When C3 is at a high level, switches 123, 153, and 173 are in the on state, and the other switches are in the off state. At this time, the gain of the first amplifier section 10 is according to the resistance value of resistor 143. Also, the frequency characteristics of the first amplifier section 10 are according to the resistance value of resistor 113, the capacitance value of capacitor element 133, and the current value of current source 163.

[0066] In this configuration, let the three gains to be selectively set in the first amplifier section 10 be G 1,1 ~G 1,3 respectively. The gain of the first amplifier section 10 can be set to G 1,1 by the resistance value of resistor 111, the capacitance value of capacitor element 131, the resistance value of resistor 141, and the current value of current source 161, and the frequency characteristics of the first amplifier section 10 at that time can be made appropriate. The gain of the first amplifier section 10 can be set to G 1,2It can be set to that value, and the frequency characteristics of the first amplifier section 10 at that time can be made appropriate. The gain G of the first amplifier section 10 is determined by the resistance value of the resistor 113, the capacitance value of the capacitor element 133, the resistance value of the resistor 143, and the current value of the current source 163. 1,3 It can be set to that value, and the frequency characteristics of the first amplifier section 10 at that time can be made appropriate.

[0067] In this way, by changing the impedance value or current value of the elements included in the first amplifier section 10 according to the gain of the first amplifier section 10, the frequency characteristics of the first amplifier section 10 can be flattened over a wide frequency band. Note that the circuit configuration of the first amplifier section 10 is not limited to the configuration example shown in FIG. 7.

[0068] The second amplifier section 20 preferably has a circuit configuration in which the change in the circuit current when the gain changes is small. For example, a Gilbert cell mixer or the like is suitable. Since the second amplifier section 20 has such a circuit configuration, the influence on the main pole of the frequency characteristics can be reduced.

Explanation of Reference Numerals

[0069] 1... Amplifier device, 10... First amplifier section, 20... Second amplifier section, 30... Amplitude detection section, 40... Control section.

Claims

1. A first amplification unit that sets any one of a plurality of discrete gains, converts an input current signal into a voltage signal based on the set gain, and outputs the converted voltage signal; A second amplification unit that sets any one of a continuously variable gain range, amplifies the voltage signal output from the first amplification unit based on the set gain, and outputs the amplified voltage signal; An amplitude detection unit that detects the amplitude of the voltage signal output from the second amplification unit; A control unit that controls the gains of the first amplification unit and the second amplification unit so that the amplitude detected by the amplitude detection unit becomes constant; An amplification device comprising the above.

2. The control unit controls the gain of the second amplification unit so that the amplitude detected by the amplitude detection unit becomes constant, and when the gain of the second amplification unit deviates from the range of not less than a first threshold value and not more than a second threshold value within the continuously variable gain range, the gain of the first amplification unit is changed. The amplification device according to Claim 1.

3. The control unit changes the gain of the first amplification unit when a certain period has elapsed after changing the gain of the first amplification unit and the gain of the second amplification unit deviates from the range of not less than the first threshold value and not more than the second threshold value. The amplification device according to Claim 2.

4. When the gain of the second amplification unit is less than the first threshold value, the control unit changes the gain of the first amplification unit to a gain that is one setting smaller, and when the gain of the second amplification unit exceeds the second threshold value, the control unit changes the gain of the first amplification unit to a gain that is one setting larger. The amplification device according to Claim 2.

5. When the gain of the second amplification unit exceeds the first threshold value, the control unit changes the gain of the first amplification unit to a gain that is one setting smaller, and when the gain of the second amplification unit is less than the second threshold value, the control unit changes the gain of the first amplification unit to a gain that is one setting larger. The amplification device according to Claim 2.

6. When the gain of the second amplification unit is less than the first threshold value, the control unit changes the gain of the first amplification unit to a gain that is one setting smaller, and when the gain of the second amplification unit exceeds the second threshold value, the control unit changes the gain of the first amplification unit to the maximum gain. The amplification device according to Claim 2.

7. When the gain of the second amplification unit exceeds the first threshold value, the control unit changes the gain of the first amplification unit to a gain that is one setting smaller, and when the gain of the second amplification unit is less than the second threshold value, the control unit changes the gain of the first amplification unit to the maximum gain. The amplification device according to Claim 2.

8. The control unit changes the impedance value or current value of an element included in the first amplification unit according to the gain of the first amplification unit. The amplification device according to claim 1.

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