JP2003204225A - Amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an amplifier in which frequency characteristics are improved and a high gain can be obtained with low distortion. <P>SOLUTION: The amplifier A is composed of a single ended differential amplifier circuit B in which an input signal 10 is inputted to a grid 12 of a triode 1, a grid 21 of a triode 2 is grounded via a grid resistor 22, plates 13 and 23 of the triodes 1 and 2 are connected through load resistors 14 and 24 to a DC power source 20 and cathodes 15 and 25 are connected to a constant current source 26 together, and a shunt regulated push-pull circuit C in which a cathode 31 of a triode 3 is grounded via a cathode resistor 33, a plate 41 of a triode 4 is connected to a DC power source 40 and a grid 42 of the triode 4 is connected to a plate 34 of the triode 3, and a grid 35 of the triode 3 and the plate 13 of the triode 1 are connected in an AC manner. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an amplifier for amplifying an input signal.

[0002]

2. Description of the Related Art A shunt-regulated push-pull circuit having a high gain, a low distortion, and a low output impedance has been conventionally known.

[0003]

However, the above conventional technique has the following problems. (A) The shunt regulated push-pull circuit has a slightly poor distortion factor in the minute input voltage region. For example,
In the case of a vacuum tube, the distortion rate is extremely small (around 0.18%) in the small input voltage region where the output voltage is about 0.5V to 1V. However, in the very small input voltage region where the output voltage is less than 0.5V, the lower the output voltage, the larger the distortion becomes (0.4% at 0.2V).

(A) Although the shunt regulated push-pull circuit has a high gain, the gain may be insufficient depending on the circuit connected to the next stage.

(C) It is difficult to directly connect the shunt regulated push-pull circuit to the first stage circuit.

An object of the present invention is to provide an amplifier having excellent frequency characteristics and capable of obtaining high gain with low distortion.

[0007]

A shunt regulated push-pull circuit is required to be unbalanced (one side is grounded) in a shunt regulated push-pull circuit. Type differential amplifier circuit is adopted in the first stage.

A single-ended type differential amplifier circuit
An input signal is input to the input end of the first active element, the input end of the second active element is grounded via an input resistor, and the first and second
Each of the output terminals of the active element is connected to a DC power source through the first and second load resistors, and each coupling terminal of the first and second active elements is connected to a constant current source. . This single
In the end type differential amplifier circuit, the unbalanced input signal is the first
It is possible to input from the input terminal of the active element of. In addition, the single-ended type differential amplifier circuit is suitable for wide-band amplification of a minute input because the fluctuation of the power supply voltage is unlikely to appear in the output due to the circuit characteristics.

The shunt regulated push-pull circuit is constructed by electrically connecting in series a third active element that is responsible for signal amplification and a fourth active element that contributes to current synthesis. The input end of the third active element and the output end of the first active element are AC-connected or directly connected.

Since this shunt regulated push-pull circuit is adopted in the next stage which is in the small input voltage region, the signal can be amplified with a low distortion rate. Also,
Due to the circuit characteristics, it has a low output impedance, which is advantageous for wideband amplification.

Due to the above operation, the amplifier of this configuration has excellent frequency characteristics (first stage single-ended type differential amplifier circuit + second stage shunt regulated push-pull circuit) and the input signal has a low distortion rate. (Use the shunt regulated push-pull circuit in the next stage)
In addition, it can be amplified with a high amplification degree (two-stage amplification).
If the input end of the third active element and the output end of the first active element are directly connected, the frequency characteristic in the low frequency range can be improved (DC to) as compared with the case of AC connection.

(Claim 2) Since the shunt regulated push-pull circuit requires the inputs to be unbalanced (one side is grounded), a single-ended type differential amplifier circuit capable of obtaining an unbalanced output is provided. Used in the first stage.

A single ended differential amplifier circuit
An input signal is input to the input end of the first active element, the input end of the second active element is grounded via an input resistor, and the first and second
Each of the output terminals of the active element is connected to the first DC power supply through the first and second load resistors, and the coupling terminals of the first and second active elements are both connected to the constant current source. is doing.

In this single-ended type differential amplifier circuit, an unbalanced input signal can be input from the input terminal of the first active element. In addition, the single-ended type differential amplifier circuit is suitable for wide-band amplification of a minute input because the fluctuation of the power supply voltage is unlikely to appear in the output due to the circuit characteristics.

In the shunt regulated push-pull circuit, the ground side end of the third active element is grounded via a resistor, the output end of the fourth active element is connected to the second DC power source, and the fourth active element is connected. Is connected to the output end of the third active element, and the ground side end of the fourth active element is connected to the output end of the third active element via a resistor. The input end of the third active element and the output end of the first active element are AC-connected or directly connected.

Since this shunt regulated push-pull circuit is adopted in the next stage which is in the small input voltage region, the signal can be amplified with a low distortion rate. Also,
Due to the circuit characteristics, it has a low output impedance, which is advantageous for wideband amplification.

Due to the above operation, the amplifier of this configuration has excellent frequency characteristics (first stage single-ended type differential amplifier circuit + second stage shunt regulated push-pull circuit) and the input signal has a low distortion rate. (Use the shunt regulated push-pull circuit in the next stage)
In addition, it can be amplified with a high amplification degree (two-stage amplification).
If the input end of the third active element and the output end of the first active element are directly connected, the frequency characteristic in the low frequency range can be improved (DC to) as compared with the case of AC connection.

(Claim 3) Since the shunt regulated push-pull circuit requires the inputs to be unbalanced (one side is grounded), a single-ended type differential amplifier circuit capable of obtaining an unbalanced output is provided. Used in the first stage.

A single ended differential amplifier circuit
An input signal is input to the grid of the first vacuum tube, the grid of the second vacuum tube is grounded via a grid resistor,
Each plate of the second vacuum tube is connected to a DC power source via the first and second load resistors, and each cathode of the first and second vacuum tubes is connected to a constant current source.

In this single-ended type differential amplifier circuit, an unbalanced input signal can be input from the grid of the first vacuum tube. In addition, the single-ended type differential amplifier circuit is suitable for wide-band amplification of a minute input because the fluctuation of the power supply voltage is unlikely to appear in the output due to the circuit characteristics.

The shunt regulated push-pull circuit is constructed by electrically connecting in series a third vacuum tube which is responsible for signal amplification and a fourth vacuum tube which contributes to current synthesis. The grid of the third vacuum tube and the plate of the first vacuum tube are AC-connected or directly connected.

Since this shunt regulated push-pull circuit is adopted in the next stage which is in the small input voltage region, the signal can be amplified with a low distortion rate. Also,
Due to circuit characteristics, low output impedance (for example, several kΩ)
It has excellent frequency characteristics.

By the above-mentioned operation, the amplifier of this structure is excellent in frequency characteristics (for example, up to 1 MHz), and is capable of amplifying an input signal with a low distortion rate (for example, 0.2% in total) and a high amplification degree. You can If the grid of the third vacuum tube and the plate of the first vacuum tube are directly connected,
The frequency characteristics in the low frequency band can be improved (DC to) as compared with the case where AC connection is performed.

(Claim 4) Since the shunt regulated push-pull circuit requires the inputs to be unbalanced (one side is grounded), a single-ended type differential amplifier circuit capable of obtaining an unbalanced output is provided. Used in the first stage.

A single-ended type differential amplifier circuit
An input signal is input to the grid of the first vacuum tube, the grid of the second vacuum tube is grounded via a grid resistor,
Each plate of the second vacuum tube is connected to the first DC power source via the first and second load resistors, and each cathode of the first and second vacuum tubes is connected to a constant current source. There is.

In this single-ended type differential amplifier circuit, an unbalanced input signal can be input from the grid of the first vacuum tube. In addition, the single-ended type differential amplifier circuit is suitable for wide-band amplification of a minute input because the fluctuation of the power supply voltage is unlikely to appear in the output due to the circuit characteristics.

In the shunt regulated push-pull circuit, the cathode of the third vacuum tube is grounded through the cathode resistance, the plate of the fourth vacuum tube is connected to the second DC power source, and the grid of the fourth vacuum tube is connected. Is connected to the plate of the third vacuum tube, and the cathode of the fourth vacuum tube is connected to the plate of the third vacuum tube via the cathode resistance. The grid of the third vacuum tube and the plate of the first vacuum tube are AC-connected or directly connected.

Since this shunt regulated push-pull circuit is adopted in the next stage which is in the small input voltage region, the signal can be amplified with a low distortion rate. Also,
Due to the circuit characteristics, it has a low output impedance, so it has excellent frequency characteristics.

By the above-mentioned operation, the amplifier of this structure is excellent in frequency characteristics (for example, up to 1 MHz), and is capable of amplifying an input signal with a low distortion rate (for example, 0.2% in total) and a high amplification degree. You can If the grid of the third vacuum tube and the plate of the first vacuum tube are directly connected,
The frequency characteristics in the low frequency band can be improved (DC to) as compared with the case where AC connection is performed.

(Claim 5) In the amplifier of claim 2, negative feedback can be applied from the fourth active element to the input terminal of the second active element, which lowers the output impedance and further increases the output impedance. Broadband can be achieved. Also,
In the amplifier according to the fourth aspect, the negative feedback can be applied from the cathode of the fourth vacuum tube to the grid of the second vacuum tube, whereby the output impedance is lowered and the band is further widened.

(Claim 6) In the amplifier of claim 4 or claim 5, the cathode resistance of the third vacuum tube is made larger than the cathode resistance of the fourth vacuum tube,
Moreover, each of the third and fourth vacuum tubes of the shunt regulated push-pull circuit is configured by connecting a plurality of vacuum tubes in parallel.

As a result, the terminal voltage of the cathode resistance of the cathode of the third vacuum tube increases (because the current doubles). Therefore, the plate voltage of the first and third vacuum tubes of the single-ended differential amplifier circuit can be set high, and the grid of the third vacuum tube and the plate of the first vacuum tube can be easily directly connected. it can.

(Claim 7) In the amplifier of claim 1 or claim 2, each active element of the single-ended type differential amplifier circuit or the shunt regulated push-pull circuit is constituted by an FET or a transistor. May be. In this way, it operates at a low voltage, the occupied volume can be reduced, and modularization is possible.

[0034]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An amplifier A (corresponding to claims 1 to 5) according to a first embodiment of the present invention will be described with reference to FIG. The amplifier A includes a single-ended type differential amplifier circuit B having a triode 1 (first active element, first vacuum tube) and a triode 2 (second active element, second vacuum tube), and a triode 3 ( Third active element, third vacuum tube) and triode 4
(Fourth active element, fourth vacuum tube) and a shunt regulated push-pull circuit C.

A grid resistor 11 is connected between the grid 12 of the triode 1 and the ground to input an input signal. The grid 21 of the triode 2 is grounded via a grid resistor 22.

The plates 13 and 23 of the triodes 1 and 2 are connected to a DC power source 20 (first DC power source) via load resistors 14 and 24 (first and second load resistors). Further, the cathodes 15 and 25 are both connected to a constant current source 26.

Between the cathode 31 of the triode 3 and the ground,
Cathode resistor 3 with bypass capacitor 32 connected in parallel
3 is connected. Further, a grid resistor 36 is connected between the grid 35 and the ground. Then, the grid 35 of the triode 3 and the plate 13 of the triode 1 are AC-connected via the coupling capacitor 37.

The plate 41 of the triode 4 is a DC power source 40.
(Second DC power supply). Further, the grid 42 is connected to the plate 34 of the triode 3. The cathode 43 of the triode 4 is connected to the plate 34 of the triode 3 via a cathode resistor 44.

Then, one end of a DC cut capacitor 45 is connected to the cathode 43 of the triode 4, and a load resistor 46 is connected between the other end of the capacitor 45 and the ground.
The output terminals 47 and 48 to which the load is connected are selected according to the type of load connected to the next stage.

When negative feedback is applied, the negative feedback circuit 50 is connected as shown by the broken line in FIG. 1, and the cathode 43 of the triode 4 is applied to the grid 21 of the triode 2. In addition,
Reference numeral 51 is a capacitor for cutting a direct current component, and 52 is a resistor for negative feedback.

The amplifier A of this embodiment has the following advantages. [A] Since the single-ended type differential amplifier circuit B is adopted in the first stage, the unbalanced input signal 10 can be input from the grid 12 of the triode 1, and the unbalanced output signal can be input to the triode 1. It can be taken out from the plate 13.

Further, the single-ended type differential amplifier circuit B is suitable for a wide band amplification of a minute input because the fluctuation of the power supply voltage hardly appears in the output due to the circuit characteristics. In addition, the load resistances 14 and 24 are reduced in resistance value to maximize the bandwidth.

Since the shunt regulated push-pull circuit C is adopted in the next stage which is in the small input voltage region, the signal can be amplified with a low distortion rate.
In addition, due to circuit characteristics, low output impedance (tens of k
Ω), it has excellent frequency characteristics.

By the above operation, the amplifier A of this embodiment is
With excellent frequency characteristics (several tens of Hz to 1 MHz),
The input signal can be amplified with a low distortion rate (total 0.2%) and a high amplification degree.

[I] Since the shunt regulated push-pull circuit C is adopted in the next stage, the output terminal 4
7-Ground or output terminal 48-Ground is excellent in the degree of freedom of the load connected, and the impedance is several tens of kΩ ~
It is possible to connect ones in the range of several hundreds kΩ.

[U] As shown by the broken line in FIG. 1, the negative feedback circuit 5
If 0 is connected and negative feedback is applied, the output impedance can be lowered and a wider band can be achieved.

Next, an amplifier D (corresponding to claims 1 to 6) according to the second embodiment of the present invention will be described with reference to FIG. The amplifier D is a single-ended differential amplifier circuit B having a triode 1 (first active element, first vacuum tube) and a triode 2 (second active element, second vacuum tube); a triode 6; 7 (third active element, third vacuum tube) and triodes 8, 9 (fourth active element, fourth vacuum tube) and a shunt regulated push-pull circuit E.

The triodes 6 and 7 connect the grids 61 and 71, the plates 62 and 72, and the cathodes 63 and 73 to each other to form one triode electrically. Further, a cathode resistor 65 having a bypass capacitor 64 connected in parallel is connected between the cathodes 63 and 73 of the triodes 6 and 7 and the ground. Also, the grids 61, 71 of the triodes 6, 7
Is directly connected to the plate 13 of the triode 1.

Also in the triodes 8 and 9, the grids 81 and 91, the plates 82 and 92, and the cathodes 83 and 93 are connected to each other to electrically form one triode. The plates 82 and 92 of the triodes 8 and 9 are DC power sources 40 (second DC power source).
It is connected to the. Also, the grid 8 of the triodes 8 and 9
1, 91 are connected to the plates 62, 72 of the triodes 6, 7.

The cathodes 83 and 93 of the triodes 8 and 9 are connected to the plate 62 of the triodes 6 and 7 via the cathode resistance 84.
It is connected to 72.

Then, the cathodes 83, 9 of the triodes 8, 9
Connect one end of the DC cut capacitor 45 to 3,
A load resistor 46 is connected between the other end of the capacitor 45 and the ground. Depending on the type of load connected to the next stage,
The output terminals 47 and 48 to which the load is connected are selected.

When negative feedback is applied, the negative feedback circuit 50 is connected as shown by the broken line in FIG. 2, and the cathodes 83 and 93 of the triodes 8 and 9 are applied to the grid 21 of the triode 2. Incidentally, as in the first embodiment, 51 is a capacitor for cutting a direct current component, and 52 is a resistor for negative feedback.

The amplifier D of this embodiment has the following advantages. [E] Similar to the amplifier A, since the single-ended type differential amplifier circuit B is adopted in the first stage, the unbalanced input signal 10 can be input from the grid 12 of the triode 1,
Moreover, an unbalanced output signal can be taken out from the plate 13 of the triode 1.

Further, the single-ended type differential amplifier circuit B is suitable for wide-band amplification of a minute input because the fluctuation of the power supply voltage hardly appears in the output due to the circuit characteristics. In addition, the load resistances 14 and 24 are reduced in resistance value to maximize the bandwidth.

The shunt regulated push-pull circuit D in which the triodes 6 and 7 are electrically one triode and the triodes 8 and 9 are electrically one triode is adopted in the next stage which is a small input voltage region. Therefore, the signal can be amplified with a low distortion rate. Moreover, since the output impedance is lower than that of the amplifier A due to the parallel connection, the frequency characteristic is excellent.

In addition to this, in the amplifier D of this embodiment, the grids 61 and 71 are directly connected to the plate 13 of the triode 1. With the above configuration, the amplifier D of this embodiment has excellent frequency characteristics (DC to 1 MHz) and can amplify the input signal with a low distortion rate (total 0.2%) and a high amplification degree. .

[O] Since the triodes 6 and 7 are electrically one triode and the triodes 8 and 9 are electrically one triode, the shunt regulated push-pull circuit D is adopted in the next stage. , The output terminal 47 and the ground, or the output terminal 48 and the ground are excellent in the degree of freedom of the load connected, and the impedance of several kΩ to several hundred kΩ can be connected.

[Ka] As shown by the broken line in FIG. 2, the negative feedback circuit 5
If 0 is connected and negative feedback is applied, the output impedance can be lowered and a wider band can be achieved.

The present invention includes the following embodiments in addition to the above embodiments. a. In the amplifier D of the second embodiment, the triode 6 and the triode 8 are used to directly connect the first stage shunt regulated.
If you want to use a push-pull circuit, the cathode resistance 65
To increase the voltage of the cathode 63 (+1
About 05V). However, the balance of the push-pull operation by the upper sphere and the lower sphere is slightly disturbed, and the output impedance is increased.

B. As shown in FIG. 3, a filter circuit 100 having a high frequency down characteristic is inserted in a coupling portion, a negative feedback circuit 200 is designed to have a constant that boosts a low frequency band, and the total frequency characteristic of an amplifier F is changed to a RIAA characteristic. You may make it become.

C. As shown in FIG. 4, the negative feedback circuit 30 is provided so that the total frequency characteristic of the amplifier G becomes the RIAA characteristic.
You may design 0. Further, the mc input and the mm input may be made selectable by the switch 400.

D. Even if the first and second active elements of the single-ended differential amplifier circuit and the third and fourth active elements of the shunt-regulated push-pull circuit are composed of FETs and transistors in addition to the vacuum tube. good.

E. Instead of the triode, a vacuum tube in which a tetrode or a pentode is connected in a triode may be used.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an amplifier according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of an amplifier according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of an amplifier according to another embodiment of the present invention.

FIG. 4 is a circuit diagram of an amplifier according to another embodiment of the present invention.

[Explanation of symbols]

1 triode (first active element, first vacuum tube) 2 triode (second active element, second vacuum tube) 3, 6, 7 triode (third active element, third vacuum tube) 4, 8, 9 triode (fourth active element, fourth vacuum tube) 10 input signal 12, 21 grid (input end) 13, 23 plate (output end) 14 load resistance (first load resistance) 15, 25 cathode (coupling end) ) 20 DC power supply (first DC power supply) 22 Grid resistance (input resistance) 24 Load resistance (second load resistance) 26 Constant current source 31, 63, 73 Cathode (ground side end) 33, 65 Cathode resistance (resistance) ) 34, 62, 72 plate (output end) 35, 61, 71 grid (input end) 40 DC power supply (second DC power supply) 41, 82, 92 plate (output end) 42, 81, 91 grid (input end) ) 43, 3,93 cathode (the ground side terminal) 44, 84 cathode resistance (resistance) A, D, F, G amplifier B single-ended type differential amplifier circuit C, E shunt regulators federated push-pull circuit

Continued front page    F term (reference) 5J090 AA01 AA15 CA21 CA35 CA61                       FA15 GN01 GN06 HA02 HA09                       HA25 HA29 HA46 KA02 KA05                       MA00 MA13 MA22                 5J091 AA01 AA15 CA21 CA35 CA61                       FA15 HA02 HA09 HA25 HA29                       HA46 KA02 KA05 MA00 MA13                       MA22                 5J500 AA01 AA15 AC21 AC35 AC61                       AF15 AH02 AH09 AH25 AH29                       AH46 AK02 AK05 AM00 AM13                       AM22

Claims (7)

[Claims] 1. An input signal is input to an input terminal of a first active element, an input terminal of a second active element is grounded via an input resistor, and output terminals of the first and second active elements are connected to each other. A single-circuit that is connected to a direct-current power supply via first and second load resistors, and that the coupling ends of the first and second active elements are both connected to a constant current source.
A shunt that electrically connects an end type differential amplifier circuit, a third active element that is responsible for signal amplification, and a fourth active element that contributes to current synthesis in series.
An amplifier comprising a regulated push-pull circuit, wherein the input end of the third active element and the output end of the first active element are AC-connected or directly connected. 2. An input signal is input to the input terminal of the first active element, the input terminal of the second active element is grounded via an input resistor, and the output terminals of the first and second active elements are connected to each other. A single-ended differential amplifier circuit, which is connected to a first DC power source via first and second load resistors, and each coupling end of the first and second active elements is connected to a constant current source. , The ground side end of the third active element is grounded via a resistor,
The output end of the active element is connected to the second DC power supply, the input end of the fourth active element is connected to the output end of the third active element, and the ground side end of the fourth active element is connected. And a shunt regulated push-pull circuit connected to the output terminal of the third active element via a resistor, wherein the input terminal of the third active element and the output terminal of the first active element are connected to each other, An amplifier characterized by being connected or directly connected in an alternating current. 3. An input signal is input to the grid of the first vacuum tube, the grid of the second vacuum tube is grounded via a grid resistor, and each plate of the first and second vacuum tubes is connected to the first and second plates.
Connected to a DC power source via the load resistance of
Single-ended type differential amplifier circuit in which each cathode of each vacuum tube is connected to a constant current source, a third vacuum tube that is responsible for signal amplification, and a fourth vacuum tube that contributes to current synthesis are electrically connected in series. An amplifier configured by a regulated push-pull circuit, wherein the grid of the third vacuum tube and the plate of the first vacuum tube are AC-connected or directly connected. 4. An input signal is input to the grid of the first vacuum tube, the grid of the second vacuum tube is grounded via a grid resistor, and each plate of the first and second vacuum tubes is connected to the first and second plates.
A single-ended differential amplifier circuit in which the cathodes of the first and second vacuum tubes are both connected to a constant current source, and the cathode of the third vacuum tube. Is grounded via a cathode resistance, the plate of the fourth vacuum tube is connected to the second DC power source, the grid of the fourth vacuum tube is connected to the plate of the third vacuum tube, and the plate of the fourth vacuum tube is connected. And a shunt regulated push-pull circuit in which a cathode is connected to the plate of the third vacuum tube via a cathode resistance, and the grid of the third vacuum tube and the plate of the first vacuum tube are connected by an alternating current. An amplifier characterized by being connected to or directly connected to. 5. When negative feedback is applied, it is applied from the fourth active element to the input end of the second active element or from the cathode of the fourth vacuum tube to the grid of the second vacuum tube. Claim 2 or claim 4 characterized in that
The amplifier described in. 6. The cathode resistance of the third vacuum tube is made larger than the cathode resistance of the fourth vacuum tube,
The amplifier according to claim 4 or 5, wherein each of the third and fourth vacuum tubes of the shunt regulated push-pull circuit is configured by connecting a plurality of vacuum tubes in parallel. . 7. The single-ended differential amplifier circuit or each active element of the shunt-regulated push-pull circuit is an FET or a transistor, according to claim 1 or 2. Amplifier.