WO2011158360A1

WO2011158360A1 - Burst-mode transimpedance amplifier

Info

Publication number: WO2011158360A1
Application number: PCT/JP2010/060279
Authority: WO
Inventors: 聡吉間; 雅樹野田; 正道野上
Original assignee: 三菱電機株式会社
Priority date: 2010-06-17
Filing date: 2010-06-17
Publication date: 2011-12-22
Also published as: JP5456162B2; JPWO2011158360A1

Abstract

A burst-mode transimpedance amplifier that achieves flat frequency response characteristics in the same band throughout a receiver for any signal, regardless of input optical power level, broadens frequency range throughout the receiver, and does not cause receiving sensitivity degradation, is obtained by equipping a burst-mode transimpedance amplifier with: a level detector (14) that detects the signal amplitude level of an input signal; an equalization function-equipped amplifier (100) that adjusts amplification level in a specific frequency band and outputs a first amplified signal on the basis of the signal amplitude level detected by the level detector; an amplifier (200) that amplifies the amplitude signal to a desired amplitude and outputs a second amplified signal on the basis of the signal amplitude level detected by the level detector; and a mixer (300) that generates an output signal obtained by correcting the high-frequency band of the input signal, by mixing a first amplified signal output by the equalization function-equipped amplifier and a second amplified signal output by the amplifier.

Description

Burst equalization amplifier

The present invention relates to a burst equalization amplifier that realizes a stable frequency response characteristic for a signal of any input optical power level.

In a system in which the input signal strength to the master station side receiver is different for each slave station, such as a one-to-multiple optical communication system to which time division multiplexing is applied, as a preamplifier in the master station side receiver, A method of ensuring an input dynamic range by changing a feedback resistance value for each input signal intensity is often used (for example, Patent Document 1).

As a result, for input optical power near the minimum receiving sensitivity, increasing the feedback resistance value increases the gain and increases the output amplitude. However, since the GB product (Gain Band width product) of the preamplifier is constant, the frequency characteristic of the output signal is narrowed. Therefore, when an input optical power signal in the vicinity of the minimum reception sensitivity is input to the receiver, a waveform with a slow rise and fall is output.

On the other hand, the amplifier connected to the subsequent stage of the preamplifier always maintains a constant gain and bandwidth, amplifies the analog amplitude input signal from the preamplifier to a constant amplitude, and passes it to the subsequent circuit. (For example, Non-Patent Document 1).

Japanese Patent No. 4310871

However, the prior art has the following problems.
Since conventional amplifiers always have a constant gain and bandwidth, when a signal with a large amplitude value is input as an input signal, the output amplitude is constant and the rise / fall time is limited by a limiting operation. A fast output signal waveform can be obtained.

On the other hand, when a signal with a small rise and fall time is input as an input signal and a signal having a small amplitude value is input, the output amplitude becomes constant due to the limiting operation, but the rise and fall remains a slow signal. For this reason, when an optical power signal in the vicinity of the minimum reception sensitivity is input from the preamplifier described above, there is a problem that the gain of the entire receiver is insufficient and the reception sensitivity is deteriorated.

In a one-to-many optical communication system to which a high-speed time division multiplexing system of 10 Gb / s or more, in which it is difficult to increase the gain of the preamplifier, the identification sensitivity of the subsequent amplifier can also affect the identification sensitivity of the entire receiver. There is sex. However, since the conventional amplifier has a constant gain and band for any signal, there is a possibility that reception sensitivity is deteriorated.

The present invention has been made to solve the above-described problems, and realizes a frequency response characteristic having a flat and the same band in the entire receiver for a signal of any input optical power level. In addition, an object of the present invention is to obtain a burst equalization amplifier that realizes a wide band in the entire receiver and does not cause deterioration in reception sensitivity.

A burst equalizing amplifier according to the present invention adjusts the amplification amount of a specific frequency band based on a level detector that detects a signal amplitude level of an input signal and a signal amplitude level detected by the level detector, An amplifier with an equalizing function for outputting the amplified signal, an amplifier for amplifying the amplitude of the input signal to a desired amplitude based on the signal amplitude level detected by the level detector, and outputting a second amplified signal, etc. A mixer that generates an output signal that compensates for the high frequency band of the input signal by mixing the first amplified signal output from the amplifier with the conversion function and the second amplified signal output from the amplifier It is.

According to the burst equalizing amplifier according to the present invention, the high frequency gain of the amplifier connected to the subsequent stage of the preamplifier is instantaneously increased as compared with other frequency bands in accordance with the input signal amplitude, and the preamplifier. By compensating for the bandwidth that could not be secured in the amplifier in the subsequent stage, for the signal of any input optical power level, the entire receiver has a frequency response characteristic that is flat and has the same bandwidth, It is possible to obtain a burst equalization amplifier that realizes a wide band in the entire receiver and does not cause deterioration in reception sensitivity.

It is a block diagram of the burst equalization amplifier in Embodiment 1 of this invention. It is a block diagram of the high frequency gain variable amplifier in Embodiment 1 of this invention. It is a block diagram of the circuit relevant to the variable peaking amplifier in Embodiment 1 of this invention. It is a block diagram of the peak detection circuit in Embodiment 1 of this invention. It is a block diagram of the bottom detection circuit in Embodiment 1 of this invention. It is a conceptual diagram of the frequency response characteristic of each part in the receiver to which the burst equalizing amplifier according to Embodiment 1 of the present invention is applied. It is a block diagram of the circuit relevant to the variable peaking amplifier in Embodiment 2 of this invention. It is a block diagram of the circuit relevant to the variable peaking amplifier in Embodiment 3 of this invention. It is a block diagram of the circuit relevant to the variable peaking amplifier in Embodiment 4 of this invention. It is a block diagram of the circuit relevant to the variable peaking amplifier in Embodiment 5 of this invention. It is a block diagram of the average value detection circuit in Embodiment 5 of this invention.

Hereinafter, preferred embodiments of the burst equalization amplifier of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a burst equalization amplifier according to Embodiment 1 of the present invention. In FIG. 1, the burst equalization amplifier 1 includes a high frequency gain variable amplifier 11, a multistage amplifier 12, an output amplifier 13, and an amplitude detection circuit 14. Note that the number of connection stages of the multistage amplifier 12 is not limited to that shown in FIG. 1, and the characteristics of the burst equalizing amplifier are not lost even if the number of dependent connection stages is increased.

Alternatively, a configuration in which the multistage amplifier 12 is not present and the high-frequency gain variable amplifier 11 is directly connected to the output amplifier 13 may be employed. Further, the multistage amplifier 12 and the output amplifier 13 may not exist, and the output from the high frequency gain variable amplifier 11 may be the output of the burst equalization amplifier circuit. Further, the amplitude detection circuit 14 may be configured to detect amplitude from a single-phase signal.

FIG. 2 is a configuration diagram of the high-frequency gain variable amplifier 11 according to the first embodiment of the present invention. In FIG. 2, the high-frequency gain variable amplifier 11 includes a variable peaking amplifier 100, an amplifier 200, and a mixer 300.

The variable peaking amplifier 100 is an amplifier that can change the peaking amount of the frequency characteristic in accordance with the input signal amplitude. Here, assuming that the peaking frequency is f _BW , f _BW uses a frequency of about 0.6 to 1.0 times the baud rate. By peaking at a frequency about 0.6 to 1.0 times the baud rate, the entire receiver can have the optimum frequency characteristics that can compensate for the band limitation of the preamplifier and suppress unnecessary high-frequency noise. Obtainable.

The amplifier 200 is an amplifier that maintains a low frequency gain and has a bandwidth of about f _BW . As this amplifier 200, for example, a differential pair can be used. In addition, as the mixer 300, for example, two differential pairs having a common load resistance can be used.

FIG. 3 is a configuration diagram of a circuit related to the variable peaking amplifier 100 according to the first embodiment of the present invention. The circuit including the variable peaking amplifier 100 of the first embodiment in FIG. 3 includes a peak detection circuit 101, a bottom detection circuit 102, a current source control circuit 103,

load resistors

104a and 104b, a load inductor 105, a

differential pair transistor

106a, 106b, and a variable current source 107.

Here, the peak detection circuit 101 and the bottom detection circuit 102 correspond to the amplitude detection circuit 14 in FIG. The peak detection circuit 101 is a circuit that can instantaneously hold the mark side voltage of the input voltage signal. On the other hand, the bottom detection circuit 102 is a circuit that can instantaneously hold the space-side voltage of the input voltage signal.

FIG. 4 is a configuration diagram of the peak detection circuit 101 according to the first embodiment of the present invention. In FIG. 4, the peak detection circuit 101 includes a diode 101a, a capacitor 101b that holds a voltage, and a MOS switch 101c that can discharge the charge of the capacitor 101b by an external reset signal. With such a configuration, by accumulating the input signal voltage in the capacitor 101b, it is possible to hold the charge corresponding to the mark side voltage in a short time of several ns to several hundreds ns.

On the other hand, FIG. 5 is a configuration diagram of the bottom detection circuit 102 according to Embodiment 1 of the present invention. In FIG. 5, the bottom detection circuit 102 includes a diode 102a, a capacitor 102b that holds a voltage, and a MOS switch 102c that can discharge the charge of the capacitor 102b by an external reset signal. With such a configuration, by accumulating the input signal voltage in the capacitor 102b, it is possible to hold the charge corresponding to the space side voltage in a short time of several ns to several hundreds ns.

The current source control circuit 103 shown in FIG. 3 controls the current value of the variable current source 107 according to the input signal amplitude value determined from the peak detection circuit 101 and the bottom detection circuit 102. More specifically, the current source control circuit 103 increases the current value of the variable current source 107 when the input signal amplitude is small, and decreases the current value of the variable current source 107 when the input signal amplitude is large. Thus, the peaking amount of the frequency characteristic can be changed.

Since the peak detection circuit 101 and the bottom detection circuit 102 are capable of a high-speed response of several ns to several hundreds ns, the response in the overhead part of each upstream packet signal in the one-to-multiple optical communication system to which the time division multiplexing method is applied. It is possible enough. Further, by releasing the charges held in the

capacitors

101b and 102b of the peak detection circuit 101 and the bottom detection circuit 102 for each upstream packet signal by an external reset signal, upstream packet signals having different input optical powers are received. Even in such a case, an optimum receiver frequency characteristic can be obtained.

FIG. 6 is a conceptual diagram of the frequency response characteristics of each part in the receiver to which the burst equalizing amplifier according to Embodiment 1 of the present invention is applied. As shown in FIG. 6, since the preamplifier operates at a high gain when low optical power is input, the frequency band decreases. On the other hand, at the time of high power input, since the low gain operation is performed by suppressing the distortion amount of the output signal, the frequency band increases.

Consider a case where such a preamplifier output signal is input to the burst equalization amplifier according to the first embodiment. In this case, at the time of low optical power input, the low frequency gain is kept constant, the peaking amount is adjusted to increase the high frequency gain, and the band at the burst equalizing amplifier output is increased. On the other hand, at the time of high optical power input, the peak amount of the burst equalization amplifier is suppressed so as not to generate waveform distortion of the receiver output, and the frequency response is flat and high gain. Realize the same bandwidth as time.

As described above, according to the first embodiment, by changing the current value of the variable current source according to the input signal voltage amplitude, the high-frequency gain of the amplifier connected to the subsequent stage of the preamplifier is changed to the input signal amplitude. Accordingly, the gain is instantaneously increased as compared with other frequency bands, and the band that cannot be secured by the preamplifier can be compensated by the subsequent amplifier. As a result, for any input optical power level signal, the entire receiver has a frequency response characteristic that is flat and has the same bandwidth, and the entire receiver has a wider bandwidth, resulting in poor reception sensitivity. It is possible to obtain a burst equalizing amplifier that does not cause the problem.

Embodiment 2. FIG.
In the first embodiment, as shown in FIG. 3, the case where the peaking amount of the variable peaking amplifier 100 is changed by changing the current value of the variable current source 107 according to the input signal voltage amplitude has been described. . On the other hand, in the second embodiment, a case where the peaking amount is changed by changing the emitter resistance value connected to the

differential pair transistors

106a and 106b in the variable peaking amplifier 100 will be described.

FIG. 7 is a configuration diagram of a circuit related to the variable peaking amplifier 100 according to the second embodiment of the present invention. The circuit including the variable peaking amplifier 100 of the second embodiment in FIG. 7 includes a peak detection circuit 101, a bottom detection circuit 102, an emitter resistance control circuit 108,

load resistors

104a and 104b, a load inductor 105, a

differential pair transistor

106a, 106 b,

variable emitter resistors

109 a and 109 b, and a current source 110. Here, the peak detection circuit 101 and the bottom detection circuit 102 correspond to the amplitude detection circuit 14 in FIG.

Further, as the

variable emitter resistors

109a and 109b, for example, MOS transistors can be used. In the variable peaking amplifier 100 of the second embodiment having such a configuration, the input to the amplifier is performed by the peak detection circuit 101 and the bottom detection circuit 102 as in the variable peaking amplifier 100 of the first embodiment. The signal amplitude can be detected.

Therefore, the emitter resistance control circuit 108 can change the peaking amount by changing the emitter resistance value according to the input signal amplitude value determined from the peak detection circuit 101 and the bottom detection circuit 102. More specifically, the emitter resistance control circuit 108 sets the emitter resistance to a high resistance, thereby reducing the gain of the variable peaking amplifier and reducing the peaking amount. On the other hand, by setting the emitter resistance to a low resistance by the emitter resistance control circuit 108, the gain of the variable peaking amplifier can be increased and the peaking amount can be increased.

As in the first embodiment, the peak detection circuit 101 and the bottom detection circuit 102 can respond at a high speed of several ns to several hundreds ns. For this reason, in the one-to-many optical communication system to which the time division multiplexing system is applied, the emitter resistance change response in the overhead part of each uplink packet signal is sufficiently possible.

As described above, according to the second embodiment, by changing the emitter resistance value according to the input signal voltage amplitude, the high-frequency gain of the amplifier connected to the subsequent stage of the preamplifier is set according to the input signal amplitude. Compared with other frequency bands, the gain is increased instantaneously, and the band that cannot be secured by the preamplifier can be compensated for by the subsequent amplifier. As a result, for any input optical power level signal, the entire receiver has a frequency response characteristic that is flat and has the same bandwidth, and the entire receiver has a wider bandwidth, resulting in poor reception sensitivity. It is possible to obtain a burst equalizing amplifier that does not cause the problem.

Embodiment 3 FIG.
In the first and second embodiments, as shown in FIG. 3, the current source control circuit 103 uses the variable peaking amplifier 100 according to the input signal amplitude values detected by the peak detection circuit 101 and the bottom detection circuit 102. The case where the peaking amount is changed has been described. In contrast, in the third embodiment, instead of using the peak detection circuit 101, the bottom detection circuit 102, and the current source control circuit 103, a case where the peaking amount of the variable peaking amplifier 100 is changed by another configuration will be described. To do.

FIG. 8 is a configuration diagram of a circuit related to the variable peaking amplifier 100 according to the third embodiment of the present invention. The circuit including the variable peaking amplifier 100 according to the third embodiment in FIG. 8 includes an amplitude detection circuit 111, a hysteresis comparator 112,

load resistors

104a and 104b, a load inductor 105,

differential pair transistors

106a and 106b, and a variable current source 107. It is configured with.

Here, the amplitude detection circuit 111 corresponds to the amplitude detection circuit 14 in FIG. As the amplitude detection circuit 111, for example, the peak detection circuit 101 as shown in FIG. 4 can be used.

In the variable peaking amplifier 100 of the third embodiment having such a configuration, instead of using the peak detection circuit 101, the bottom detection circuit 102, and the current source control circuit 103, an amplitude detection circuit 111 and a hysteresis comparator 112 are provided. Thus, a variable peaking amplifier is configured to vary the peaking amount.

In the third embodiment, the hysteresis comparator 112 sets the current value of the variable current source 107 so as to perform peaking when the amplitude of the input signal to the variable peaking amplifier 100 exceeds the reference voltage input from the outside. increase. On the other hand, when the input signal amplitude is less than the reference voltage, the hysteresis comparator 112 operates the variable peaking amplifier so as to decrease the current value so as not to perform peaking. As a result, a constant frequency response characteristic can be obtained as a receiver even if the input optical power changes.

Furthermore, by using the hysteresis comparator 112, it is possible to suppress the transition between the peaking operation and the peaking avoidance operation of the variable peaking amplifier 100 even when the power suddenly changes during the packet.

Note that the amplitude detection circuit 111 is capable of a high-speed response of several ns to several hundreds ns. For this reason, in the one-to-many optical communication system to which the time division multiplexing system is applied, a response in the overhead part of each uplink packet signal is sufficiently possible.

As described above, according to the third embodiment, by using the hysteresis comparator, the current value of the variable current source is changed in accordance with the input signal voltage amplitude, so that the high frequency of the amplifier connected to the subsequent stage of the preamplifier. The gain is instantaneously increased in comparison with other frequency bands in accordance with the input signal amplitude, and a band that cannot be secured by the preamplifier can be compensated for in the subsequent amplifier. As a result, for any input optical power level signal, the entire receiver has a frequency response characteristic that is flat and has the same band, and the entire receiver has a wider bandwidth, resulting in poor reception sensitivity. It is possible to obtain a burst equalizing amplifier that does not cause the problem.

Embodiment 4 FIG.
In the third embodiment, the case where the peaking amount of the variable peaking amplifier is determined by one hysteresis comparator 112 has been described. On the other hand, in the fourth embodiment, a case where the peaking amount can be finely adjusted using a plurality of hysteresis comparators will be described.

FIG. 9 is a configuration diagram of a circuit related to the variable peaking amplifier 100 according to the fourth embodiment of the present invention. The circuit including the variable peaking amplifier 100 of the fourth embodiment in FIG. 9 includes an amplitude detection circuit 111, n hysteresis comparators 112 (1) to 112 (n),

load resistors

104a and 104b, load inductor 105, differential A pair of

transistors

106a and 106b and a variable current source 107 are provided.

In the variable peaking amplifier 100 of the third embodiment having such a configuration, a plurality of different voltages are held as reference voltages of the hysteresis comparators 112 (1) to 112 (n) prepared in advance. Thereby, a plurality of threshold values of the input signal amplitude can be provided. By changing the current value of the variable peaking amplifier 100 based on the outputs of the hysteresis comparators 112 (1) to 112 (n), it is possible to compare with the case of the third embodiment using a single hysteresis comparator 112. Thus, the peaking amount can be finely adjusted.

Further, by using the hysteresis comparators 112 (1) to 112 (n), the transition between the peaking operation and the peaking avoidance operation of the variable peaking amplifier 100 can be suppressed even when the power suddenly changes during the packet. It becomes possible.

It should be noted that the amplitude detection circuit 111 can respond at a high speed of several ns to several hundreds ns. For this reason, in the one-to-many optical communication system to which the time division multiplexing method is applied, a response in the overhead part of each uplink packet signal is sufficiently possible.

As described above, according to the fourth embodiment, by providing a plurality of hysteresis comparators, it becomes possible to finely adjust the peaking amount as compared with the case of using one hysteresis comparator.

Embodiment 5 FIG.
In the first to fourth embodiments, the case where the peaking amount of the variable peaking amplifier 100 is determined using the peak detection circuit 101 or the amplitude detection circuit 111 has been described. On the other hand, in the fifth embodiment, the case where the peaking amount is made variable by detecting the average value of the input signal and detecting the signal amplitude based on the difference from the signal off-level voltage input from the outside will be described. To do.

FIG. 10 is a configuration diagram of a circuit related to the variable peaking amplifier 100 according to the fifth embodiment of the present invention. The circuit including the variable peaking amplifier 100 of the fifth embodiment in FIG. 10 includes an average value detection circuit 113, a current source control circuit 103,

load resistors

104a and 104b, a load inductor 105, a

differential pair transistors

106a and 106b, and a variable A current source 107 is provided. Here, the average value detection circuit 113 corresponds to the amplitude detection circuit 14 in FIG.

In the variable peaking amplifier 100 of the fifth embodiment having such a configuration, the peaking amount is variable using the average value detection circuit 113. FIG. 11 is a configuration diagram of the average value detection circuit 113 according to the fifth embodiment of the present invention. The average value detection circuit 113 shown in FIG. 11 includes a resistor 113a and a capacitor 113b, and can output an average voltage of an input signal by taking the form of an LPF.

In the fifth embodiment, the average value of the input signal is detected using the average value detection circuit 113, and the input signal amplitude value is detected from the difference between the detected average value and the signal off-level voltage input from the outside. Here, the average value detection circuit 113 always continues to detect the average value of the input signal. For this reason, the peaking amount of the amplifier can be continuously changed, and an operation can be performed for any signal amplitude without an external reset signal.

Note that the average value detection circuit 113 is capable of high-speed response of several hundred ns. For this reason, in the one-to-many optical communication system to which the time division multiplexing method is applied, a response in the overhead part of each uplink packet signal is sufficiently possible.

As described above, according to the fifth embodiment, the input signal amplitude value is constantly calculated using the average value detection circuit. As a result, the peaking amount of the amplifier can be continuously changed, and a burst equalizing amplifier that can operate for any signal amplitude without an external reset signal can be obtained.

In the above-described third to fifth embodiments, the peaking amount of the variable peaking amplifier 100 is changed by changing the current value of the variable current source 107 in accordance with the input signal voltage amplitude, as in the first embodiment. Explained the case of changing. However, in the inventions according to the third to fifth embodiments, the peaking is obtained by changing the emitter resistance values connected to the

differential pair transistors

106a and 106b in the variable peaking amplifier 100 as in the second embodiment. The amount can be changed, and the same effect can be obtained.

Claims

A level detector for detecting the signal amplitude level of the input signal;
Based on the signal amplitude level detected by the level detector, the amount of amplification in a specific frequency band is adjusted, and an amplifier with an equalizing function for outputting a first amplified signal;
An amplifier that amplifies the amplitude of the input signal to a desired amplitude based on the signal amplitude level detected by the level detector and outputs a second amplified signal;
By mixing the first amplified signal output from the amplifier with the equalizing function and the second amplified signal output from the amplifier, an output signal that compensates for the high frequency band of the input signal is generated. A burst equalizing amplifier characterized by comprising:
The burst equalization amplifier according to claim 1,
The amplifier with equalization function is configured to include a differential amplifier, and can adjust the amplification amount of the characteristic frequency band by applying a resistor and an inductor as a load of the differential amplifier, and the level detector A burst equalizing amplifier characterized in that the first amplified signal is output by adjusting a current amount of the differential amplifier based on the signal amplitude level detected in step (1).
The burst equalization amplifier according to claim 1,
The amplifier with equalization function is configured to include a differential amplifier, and can adjust the amplification amount of the characteristic frequency band by applying a resistor and an inductor as a load of the differential amplifier, and the level detector The first amplified signal is output by adjusting a resistance value of an emitter resistor added to each differential transistor of the differential amplifier based on the signal amplitude level detected in step B. Amplifier.
The burst equalizing amplifier according to any one of claims 1 to 3,
The level detector is configured to have a peak detection circuit and a bottom detection circuit, and detects the signal amplitude level.
The burst equalization amplifier according to claim 2,
The amplifier with equalization function includes a hysteresis comparator that adjusts the amount of current of the differential amplifier based on a comparison result between an output voltage corresponding to the signal amplitude level detected by the level detector and a reference voltage. A burst equalizing amplifier characterized by the following.
The burst equalization amplifier according to claim 3,
The amplifier with equalization function includes a hysteresis comparator that adjusts a resistance value of the emitter resistor based on a comparison result between an output voltage corresponding to the signal amplitude level detected by the level detector and a reference voltage. Features a burst equalization amplifier.
The burst equalization amplifier according to claim 5,
The hysteresis comparator includes a plurality of hysteresis comparators, and a comparison result between an output voltage corresponding to the signal amplitude level detected by the level detector and a plurality of reference voltages corresponding to each of the plurality of hysteresis comparators. A burst equalizing amplifier characterized in that the amount of current of the differential amplifier is adjusted in multiple stages based on the above.
The burst equalization amplifier according to claim 6,
The hysteresis comparator includes a plurality of hysteresis comparators, and a comparison result between an output voltage corresponding to the signal amplitude level detected by the level detector and a plurality of reference voltages corresponding to each of the plurality of hysteresis comparators. A burst equalizing amplifier characterized in that the resistance value of the emitter resistor is adjusted in multiple stages based on the above.
The burst equalizing amplifier according to any one of claims 1 to 3,
The level detector includes an average value detection circuit that detects an average value of the amplitude of the input signal as the signal amplitude level, and detects the signal amplitude level.
The amplifier with equalization function is configured to perform the second amplification based on a difference between an off-level signal voltage input from the outside and an output signal voltage corresponding to the signal amplitude level detected by the average value detection circuit. A burst equalization amplifier characterized by adjusting an amplification amount of the specific frequency band by outputting a signal.