buffer

Abstract

To enhance an amplification factor in a high frequency range, compared with a conventional buffer.SOLUTION: A buffer is disposed between an electronic musical instrument and an amplifier. The buffer comprises a high input impedance part, an amplification part, and a low output impedance part. The high input impedance part uses a field effect transistor which has high input impedance, and to which signals from the electronic musical instrument side are inputted. The amplification part amplifies an output from the high input impedance part with the use of a transistor, and at the same time, it enhances an amplification factor in a high frequency range with the use of a high range resistor and a high range capacitor connected in series to each other. The low output impedance part uses a transistor which has low output impedance and outputs an output from the amplification part to the amplifier side.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a buffer that is placed between an electronic musical instrument and an amplifier. [Background technology]

[0002] In the case of electronic musical instruments that pick up the vibration of strings, such as guitars, the output signal from the electronic musical instrument is small, so the frequency characteristics of the signal are easily affected by the cable between the electronic musical instrument and the amplifier. The technology described in Non-Patent Document 1 is known as a conventional technology for reducing this effect. FIG. 1 is a diagram showing a configuration when an electronic musical instrument (e.g., guitar) and an amplifier are connected with a shielded cable. FIG. 2 is a diagram showing a configuration in which a conventional buffer is added to the configuration of FIG. 1. The conventional buffer increases the input impedance and decreases the output impedance, making the characteristics of the input signal less susceptible to the effects of the cable length and the amplifier's input impedance.

[0003] In FIG. 1, an electronic musical instrument 910 and an amplifier 930 are connected by cores 921 and 922 of a shielded cable. Between the cores 921 and 922, there exists a capacitance 923 proportional to the length of the cable. In the example of FIGS. 1 and 2, the capacitance 923 is (180×L) pF when the length is Lm. The input impedance 931 of the amplifier 930 is also shown. In the buffer 800 illustrated in FIG. 2, the core 921 is at ground potential. After passing through a resistor 821 and a capacitor 822, the input signal is biased by a power supply unit 831 and a resistor 832 and input to the gate of a field effect transistor 810. A voltage is applied to the drain of the field effect transistor 810 by a power supply unit 811, and a resistor 812 is arranged between the source and the ground potential. A capacitor 841 and a resistor 842 are arranged in series between the source and the output of the buffer. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Toshihiko Arai (101010.fun), “Idea Note, The Simplest FET Buffer Circuit (Effector Construction)”, [Retrieved December 6, 2021], Internet<https: / / 101010.fun / analog / simplest-fet-buffer.html> . Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional buffers realize high input impedance and low output impedance, and can faithfully output the input signal. However, the conventional technology has a problem in that it does not improve the frequency characteristics on the high frequency side. The present invention aims to increase the amplification rate in the high frequency region more than conventional buffers. [Means for solving the problem]

[0006] The buffer of the present invention is placed between an electronic musical instrument and an amplifier. The buffer of the present invention comprises a high input impedance section, an amplifier section, and a low output impedance section. The high input impedance section has high input impedance and uses a field effect transistor to which a signal is input from the electronic musical instrument. The amplifier section amplifies the output from the high input impedance section using a transistor, and improves the amplification factor in the high frequency range by a high frequency resistor and a high frequency capacitor connected in series. The low output impedance section has low output impedance and uses a transistor that outputs the output from the amplifier section to the amplifier side. Effect of the Invention

[0007] According to the buffer of the present invention, the amplifier section amplifies the output from the high input impedance section using a transistor, and improves the amplification factor in the high frequency range by using a high frequency resistor and a high frequency capacitor connected in series, thereby making it possible to increase the amplification factor in the high frequency range more than conventional buffers. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a configuration when an electronic musical instrument and an amplifier are connected with a shielded cable. [Diagram 2] FIG. 1 shows a configuration in which a conventional buffer is added. [Diagram 3] FIG. 2 is a diagram showing a configuration in which a buffer according to the present invention is added to the configuration shown in FIG. [Figure 4] FIG. 2 is a diagram showing an example of the configuration of an electronic musical instrument used in a simulation. [Diagram 5] FIG. 13 is a diagram showing a simulation result for comparing the conventional technology with the present invention. [Figure 6] An enlarged view of the X part to compare (B), (C), and (D) in Figure 5. [Figure 7] FIG. 13 is a diagram showing a simulation result when values ​​of some resistors and capacitors of the buffer of the present invention are changed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described in detail. Note that components having the same functions are given the same reference numbers and duplicated explanations will be omitted. EXAMPLES

[0010] FIG. 3 is a diagram showing a configuration in which a buffer of the present invention is added to FIG. 1. The buffer 100 is placed between an electronic musical instrument 910 and an amplifier 930. The electronic musical instrument 910 is assumed to be an electronic musical instrument with a weak output signal, such as a guitar or bass that picks up the vibration of strings. The buffer 100 includes a high input impedance section, an amplifier section, and a low output impedance section. The high input impedance section has a high input impedance and uses a field effect transistor 110 to which a signal is input from the electronic musical instrument side. The amplifier section amplifies the output from the high input impedance section using an amplifier transistor 130, and improves the amplification factor in the high frequency range by a high frequency resistor 141 and a high frequency capacitor 142 connected in series. The low output impedance section has a low output impedance and uses a low output impedance transistor 170 that outputs the output from the amplifier section to the amplifier side.

[0011] The buffer 100 illustrated in FIG. 3 will be described in more detail. The buffer 100 includes a field effect transistor 110, an amplifying transistor 130, a low output impedance transistor 170, and power supply units 111 and 112. A signal is input to the field effect transistor 110 from the electronic musical instrument 910. The amplifying transistor 130 improves the amplification factor in the high frequency range using a high frequency resistor 141 and a high frequency capacitor 142 connected in series. The low output impedance transistor 170 outputs a signal corresponding to the potential of the collector of the amplifying transistor 130 to the amplifier side. The power supply unit 111 supplies a positive potential (+15V in FIG. 3) with respect to the ground potential, and the power supply unit 112 supplies a negative potential (-14V in FIG. 3) with respect to the ground potential. The core wire 921 is at the ground potential.

[0012] The drain of the field effect transistor 110 is connected to a positive potential via a first resistor 131, and the source is connected to a negative potential via second resistors 113 and 114. A signal from the electronic musical instrument, which has been voltage-divided by two input resistors 121 and 122, is input to the gate. More specifically, one end of the input resistor 121 is connected to the core 922, and the other end is connected to the gate of the field effect transistor 110. One end of the input resistor 122 is connected to the gate of the field effect transistor 110, and the other end is at ground potential. In the case of FIG. 3, the field effect transistor 110, the first resistor 131, the second resistors 113 and 114, and the input resistors 121 and 122 form a high input impedance section.

[0013] The amplifying transistor 130 in Fig. 3 is of a PNP type, and has an emitter connected to a positive potential (+15V) and a collector connected to the source of the field effect transistor 110 via a third resistor 132. The base of the amplifying transistor 130 is connected to the drain of the field effect transistor 110. Also, a high frequency resistor 141 and a high frequency capacitor 142 connected in series have one end connected to a ground potential and the other end connected to the collector of the amplifying transistor 130 via the third resistor 132. In the case of Fig. 3, the amplifying transistor 130, the first resistor 131, the third resistor 132, the high frequency resistor 141, the high frequency capacitor 142, and the second resistors 113 and 114 constitute an amplifying section. Note that some resistors overlap with the high input impedance section.

[0014] The collector current of the amplifying transistor 130 flows to a negative potential via the second resistors 113 and 114. A current from the source of the field effect transistor 110 also flows through the second resistors 113 and 114. Since both currents flow through the second resistors 113 and 114, the potential at C in FIG. 3 becomes high even if the collector current of the amplifying transistor 130 is small. Therefore, by connecting the collector of the amplifying transistor 130 to the source of the field effect transistor 110 via the third resistor 132, it is possible to obtain an energy saving effect. In addition, the high frequency resistor 141 and the high frequency capacitor 142 connected in series can increase the amplification factor in the high frequency range.

[0015] The low output impedance transistor 170 is an NPN type, with its collector connected to a positive potential (+15V) and its emitter connected to a negative potential (-14V) via a fourth resistor 171. The base of the low output impedance transistor 170 is connected to the collector of the amplifying transistor 130. One end of an output capacitor 172 and an output resistor 173 connected in series is connected to the emitter of the low output impedance transistor 170, and the other end is connected to the output terminal of the buffer 100. That is, a signal corresponding to the potential of the collector of the amplifying transistor 130 is output from the buffer 100. The low output impedance transistor 170, the fourth resistor 171, the output capacitor 172, and the output resistor 173 constitute a low output impedance section.

[0016] In addition, in FIG. 3, an electromagnetic noise capacitor 181, a power supply noise capacitor 151, and a potential stabilization resistor 161 are also arranged. The electromagnetic noise capacitor 181 is arranged between the drain of the field effect transistor 110 and the collector of the amplifying transistor 130. The electromagnetic noise capacitor 181 can reduce high-frequency electromagnetic noise. The power supply noise capacitor 151 is arranged between a negative potential (−14V) and a ground potential via a second resistor 114 (a part of the second resistor). In other words, one end of the power supply noise capacitor 151 is connected to a connection part between the second resistor 113 and the second resistor 114, and the other end is grounded. The power supply noise capacitor 151 can reduce high-frequency noise contained in the power supply units 111 and 112. The potential stabilization resistor 161 is arranged between the collector of the amplifying transistor 130 and the ground potential. The potential stabilization resistor 161 can stabilize the potential of the collector of the amplifying transistor 130 corresponding to the output from the buffer 100.

[0017] 4 shows an example of the configuration of an electronic musical instrument (such as a guitar) used in the simulation. An AC power supply 901 is connected to the electronic musical instrument 910. A core wire 921 is grounded. A coil 911, a resistor 912, and a capacitor 913 correspond to a signal pickup mechanism. A variable resistor 914 and a capacitor 915 correspond to a tuner. A variable resistor 916 corresponds to a volume control section. In the simulation, the coil 1 was set to 2.75H, the resistor 912 to 12kΩ, the capacitor 913 to 120pF, the variable resistor 914 to 250kΩ, the capacitor 915 to 0.047μF, and the variable resistor 916 to 250kΩ. The input impedance 931 of the amplifier 930 was set to 1MΩ.

[0018] FIG. 5 shows the results of a simulation for comparing the prior art and the present invention. FIG. 6 is an enlarged view of the X portion for comparing (B), (C), and (D) of FIG. 5. The horizontal axis of FIG. 5 and FIG. 6 is frequency, and the vertical axis is signal strength. FIG. 5 (A) shows the frequency characteristic of the voltage at the input impedance 931 when L=0 in FIG. 1. In other words, it shows the output of the electronic musical instrument 910 itself. In the case of (A), the capacitance 923 is 0 pF. FIG. 5 and FIG. 6 (B) shows the frequency characteristic of the voltage at the input impedance 931 when L=3(m) in FIG. 1. In other words, it shows the input signal to the amplifier when it is affected by a 3m long shielded cable. FIG. 5 and FIG. 6 (C) shows the frequency characteristic of the voltage at the input impedance 931 when L=3(m) in FIG. 2. FIG. 5 and FIG. 6 (D) shows the frequency characteristic of the voltage at the input impedance 931 when L=3(m) in FIG. 3. In cases (B) to (D), the capacitance 923 is 540 pF.

[0019] In the simulation, in buffer 800 in FIG. 2, resistor 821 was set to 1 kΩ, capacitor 822 to 1 μF, resistor 832 to 1 MΩ, power supply unit 831 to a 4 V DC power supply, power supply unit 811 to an 8 V DC power supply, resistor 812 to 10 kΩ, capacitor 841 to 1 μF, and resistor 842 to 1 kΩ.

[0020] In the simulation whose results are shown in (D) of Figures 5 and 6, the power supply, resistors, capacitors, etc. shown in Figure 3 were set as follows: the power supply unit 111 was a 15V DC power supply, and the power supply unit 112 was a 14V DC power supply. The first resistor 131 was 1kΩ, the second resistor 113 was 22kΩ, the second resistor 114 was 470Ω, the input resistor 121 was 1kΩ, the input resistor 122 was 1MΩ, the third resistor 132 was 3.3kΩ, the high-frequency resistor 141 was 47kΩ, the high-frequency capacitor 142 was 0.001μF, the fourth resistor 171 was 10kΩ, the output capacitor 172 was 1μF, the output resistor 173 was 1kΩ, the electromagnetic noise capacitor 181 was 330pF, the power supply noise capacitor 151 was 100μF, and the potential stabilization resistor 161 was 1MΩ. However, these values ​​are examples and different resistance values ​​may be used.

[0021] In FIG. 6, (B1) shows the intensity of the 100 Hz signal in (B), (C1) shows the intensity of the 100 Hz signal in (C), and (D1) shows the intensity of the 100 Hz signal in (D). It can be seen that the high-frequency side frequency that has the same intensity as the 100 Hz signal is the same in (B) and (C). In other words, it can be seen that even if the buffer 800 shown in FIG. 2 is used, the amplification factor of the high-frequency region does not change compared to the low-frequency region. On the other hand, in (D), the frequency on the high-frequency side that has the same intensity as the 100 Hz signal is higher by W, so it can be seen that the amplification factor of the high-frequency region is higher compared to the low-frequency region. In other words, it can be seen that the buffer 100 of the present invention has a higher amplification factor in the high-frequency region than the conventional buffer 800.

[0022] FIG. 7 shows the results of a simulation in which the values ​​of some resistors and capacitors in the buffer of the present invention are changed. The horizontal axis of FIG. 7 is frequency, and the vertical axis is signal strength. (D) of FIG. 7 is the same as (D) of FIG. 5 and FIG. 6. (E) of FIG. 7 shows the frequency characteristics of a signal in which the third resistor 132 is changed. Specifically, by changing the third resistor 132 to 3.9 kΩ, the amplification factor is increased by about 0.2 dB compared to (D). (F) of FIG. 7 shows the frequency characteristics in which the third resistor 132 and the high-frequency capacitor 142 are changed. Specifically, by changing the third resistor 132 to 3.9 kΩ and the high-frequency capacitor 142 to 0.0022 μF, the amplification factor is increased by about 0.3 dB compared to (D).

[0023] According to the buffer 100, the amplifier section amplifies the output from the high input impedance section using transistors, and improves the amplification factor in the high frequency range by using a high frequency resistor and a high frequency capacitor connected in series. In addition, since only a field effect transistor and a transistor are used as active elements, noise that occurs when the circuit configuration is complex can be reduced. In other words, it is possible to increase the amplification factor in the high frequency range more than conventional buffers while keeping noise low, just like conventional buffers that employ simple circuit configurations. [Explanation of symbols]

[0024] 100 Buffer 110 Field effect transistor 111,112 Power supply section 113,114 2nd resistor 121,122 Input resistor 130 Amplification transistor 131 1st resistor 132 3rd resistor 141 High-frequency resistor 142 High-frequency capacitor 151 Power supply noise capacitor 161 Potential stabilization resistor 170 Low output impedance transistor 171 Fourth resistor 172 Output capacitor 173 Output resistor 181 Electromagnetic noise capacitor 800 Buffer 810 Field effect transistor 811,831 Power supply unit 812,821,832,842 Resistors 822,841 Capacitors 901 AC power supplies 910 Electronic musical instruments 911 Coil 912 Resistor 913,915 Capacitor 914,916 Variable resistor 921,922 Core 923 Capacitance 930 Amplifier 931 Input impedance

Claims

1. A buffer disposed between an electronic musical instrument and an amplifier, a field effect transistor to which a signal is input from an electronic musical instrument; an amplifying transistor that improves the amplification factor in the high frequency range by using a high frequency resistor and a high frequency capacitor connected in series; a low output impedance transistor for outputting a signal corresponding to the collector potential of the amplifying transistor to an amplifier; A power supply section that supplies positive and negative potentials relative to the ground potential Equipped with the field effect transistor has a drain connected to the positive potential via a first resistor, a source connected to the negative potential via a second resistor, and a gate receiving a signal from the electronic musical instrument that has been voltage-divided by two input resistors; the amplifying transistor is a PNP type, the emitter is connected to the positive potential, the collector is connected to the source of the field effect transistor via a third resistor, and the base is connected to the drain of the field effect transistor; the high-frequency resistor and the high-frequency capacitor connected in series have one end connected to a ground potential and the other end connected to the collector of the amplifying transistor via the third resistor; the low output impedance transistor is an NPN type, the collector is connected to the positive potential, the emitter is connected to the negative potential via a fourth resistor, and the base is connected to the collector of the amplifying transistor; One end of the output capacitor and output resistor connected in series is connected to the emitter of the low output impedance transistor, and the other end is connected to the output terminal of the buffer. A buffer comprising:

2. 2. The buffer of claim 1, An electromagnetic noise capacitor is disposed between the drain of the field effect transistor and the collector of the amplifying transistor. A buffer comprising:

3. 3. A buffer according to claim 1 or 2, A power supply noise capacitor is disposed between the negative potential and the ground potential via a portion of the second resistor. A buffer comprising:

4. A buffer according to any one of claims 1 to 3, A potential stabilizing resistor is disposed between the collector of the amplifying transistor and the ground potential. A buffer comprising:

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