JPS6048924B2 - Second harmonic continuously variable circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a continuous second harmonic system that can continuously change the amount of the second harmonic without changing the gain of the analog amplifier and while suppressing the generation of the third harmonic. Regarding variable circuits.

When changing the gain of an analog amplifier to adjust the sound quality or the like, there are cases where it is desired to change only the amount of the second harmonic while suppressing distortion of the third harmonic.

However, it has been extremely difficult to stably and significantly change only the second harmonic using conventional techniques. For example, the first
An analog amplifier circuit in which an attenuator 3, a distortion circuit 4, and an amplifier 5 with a gain of A are sequentially connected between an input terminal 1 and an output terminal 2 as shown in principle in the figure, or as shown in FIG. As shown in FIG. 3, a distortion circuit 6 and an amplifier 7 with a gain of A are sequentially connected between the input terminal 1 and the output terminal 2, and a feedback circuit 8 with a gain of β is provided. Input terminal 1
A resistor s, a distortion circuit 9 and a gain A are connected between the output terminal 5 and the output terminal 2.
It is conceivable to control the harmonic distortion rate using an analog amplifier circuit in which the amplifiers 10 of 10 and 10 are sequentially connected, and a feedback resistor Rf is further connected, but it is difficult with either method. In Figures 1 to 3, Alβ is the gain, Rs and Rf are linear resistances, and K, K', and K'' are the first, second, and third order derivatives of the input voltage el and the output voltage E. The coefficient is DeOd2eOd3eO, KN-K'-K'', and A≧1, Deide
, 2゛Dei3 In Fig. 2, Kβ>1, in Fig. 3, Kβ>
1+β and 5, the gain in Figure 1 is K) The gain in Figure 2 is 1, βRflll The gain in Figure 3 is ``= tiles, the harmonic distortion rate is 8, the normalized third harmonic in Figure 1 The distortion rate is the normalized second harmonic distortion rate in Figures 2 and 3, and the normalized 3rd harmonic distortion rate in Figures 2 and 3 is
The harmonic distortion rate is ~.

However, the normalized distortion rate indicates a value when the distortion rate is 1 when A=1. Therefore, by continuously changing the gain A, the harmonic distortion rate can be changed. That is, in the circuit of FIG. 1, if K''=0 and the gain A is changed, the second harmonic distortion rate changes depending on the relationship.

However, implementation is difficult due to poor temperature characteristics and the need for two variable elements, 8 and A. In addition, in order to control the second harmonic distortion while suppressing the third harmonic distortion using the circuits shown in FIGS. 2 and 3, K"=0 (
In other words, the absence of third harmonic distortion when negative feedback is not applied) is not a necessary and sufficient condition, but K-K''=3(K')
2 is a necessary condition.

If this condition is expressed as a distortion rate characteristic when negative feedback is not applied, it will be as shown in Figure 4, where the second harmonic distortion rate DB on the horizontal axis and the third harmonic distortion rate O on the vertical axis are illusory distributions of 2. It is a linear relationship. Furthermore, in addition to the above conditions, the phase fundamental wave S of the output third harmonic
There must be a relationship of -Sin3ω0t with respect to inω0t. However, it is impossible to realize a circuit that satisfies all of the above conditions using a single transistor or FET circuit, and it is also very difficult to create a multi-stage amplifier circuit. Furthermore, even if the characteristics K, K', and K'' that satisfy the condition are realized, the maximum second harmonic distortion rate when A = 1 is - when negative feedback is not applied to a constant output. It is not possible to generate a large amount of second harmonic distortion from Kβ.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a second harmonic that can easily and continuously change the second harmonic distortion rate while keeping the third harmonic distortion at a minimum without changing the gain of the analog amplifier.
The object of the present invention is to provide a continuously variable harmonic circuit.

To achieve the above object, the present invention includes an input resistor connected in series to an analog signal input terminal and corresponding to the θ resistor 14 of the embodiment, for example, and a transistor 12 of the embodiment whose base is connected to the input resistor. a 5-output resistor connected between the collector of the transistor and one bias power supply line, which corresponds to the resistor 16 in the embodiment, and the emitter of the transistor and the ground line in the embodiment, for example. An emitter current negative feedback resistor, which corresponds to the resistor 18 in the embodiment, for example, is connected between the base of the transistor and the other bias power supply line. A bias resistor corresponding to the resistor 20 of the embodiment, whose collector and base are connected to the base of the transistor, and whose emitter is connected to the other bias power supply line via the resistor and is thermally coupled to the transistor. For example, a transistor-type diode corresponding to the diode 21 of the embodiment, a differential amplifier with a low harmonic distortion rate whose one input terminal is connected to the collector of the transistor, and the other input terminal of the differential amplifier and the a fixed or variable feedback setting resistor connected between the other bias power supply line J; and a variable or fixed differential resistor connected between the output terminal of the differential amplifier and the other input terminal. It consists of an amplifier feedback resistor and a gain setting feedback resistor connected between the output terminal of the differential amplifier and the base of the transistor, and the differential amplifier feedback resistor or the feedback setting resistor of the differential amplifier is This invention relates to a second harmonic continuously variable circuit configured to change second harmonic distortion by adjustment.

According to the present invention, by adjusting the value of the current negative feedback resistor, it becomes possible to suppress the third harmonic distortion rate to, for example, −90 dB or less, and furthermore, the third harmonic distortion rate and It becomes possible to continuously and significantly change the second harmonic distortion rate while keeping the gain approximately constant.

Since this second harmonic distortion rate can be changed simply by changing the amount of feedback of the differential amplifier, circuit design and operation are easy. Furthermore, since the transistor and the transistor-type diode are thermally coupled, changes in characteristics due to Z changes in ambient temperature are extremely small. Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 5 showing a second harmonic continuously variable circuit according to an embodiment of the present invention, there is an input terminal between a signal input terminal 11 to which a low frequency analog small J signal is input and an NPN type transistor 12. A series circuit of a coupling capacitor 13 and an input resistor 14 is connected. The collector of the transistor 12 and one bias power supply line 1 for applying +Vcc
An output resistor 16 is connected between the transistor 1 and the transistor 1.
A semi-fixed emitter current negative feedback resistor 1 is connected between the emitter of 2 and the ground line 17 which is the other bias power supply line.
8 is connected, the first stage amplifier circuit including the transistor 12 has an emitter grounded. Works as an amplifier. 1
9 is an input grounding resistor connected between the signal input terminal 11 and the grounding line 17, 20 is a bias resistor connected between the power supply line 15 and the base of the transistor 12, and 21 is an NPN transistor. It is a transistor type diode in which the collector and base of the transistor are connected and the emitter junction is used as a diode.

The collector and base of this transistor type diode 21 are connected to the base of the transistor 12, respectively, and the emitter of this transistor type diode 21 is connected to the ground line 17 via a resistor 22. transistor 1
A coupling capacitor 23 and a resistor 24 are sequentially connected between the collector of the motor amplifier 2 and the ground line 17, and a difference between the two with extremely small distortion is connected to one input terminal 2 of the motor amplifier 25.
6 is connected.

The other input terminal 27 of the differential amplifier 25 and the ground line 17
A feedback setting resistor 28 of the differential amplifier is connected between the differential amplifier 25 and a feedback resistor 30 having a variable resistor configuration between the output terminal 29 of the differential amplifier 25 and the other input terminal 27. Therefore, the second stage amplifier circuit including the differential amplifier 25 works as a variable gain amplifier. A series circuit including a feedback capacitor 31 and a gain setting feedback resistor 32 is connected between the output terminal 29 of the differential amplifier 25 and the base of the transistor 12.

Therefore, now the value of the resistor 14 is Rs) and the value of the resistor 32 is Rf.
Then, the gain Rf of the entire circuit in FIG. 5 is [.

The output terminal 29 of the differential amplifier 25 is connected to the output coupling capacitor 3.
3 to the output terminal 34 , and an output grounding resistor 35 is connected between the output terminal 34 and the grounding line 17 . To illustrate the values of each part of the circuit in FIG. 5, the resistor 14
is 12kΩ, resistor 16 is 4.7kΩ, resistor 18 is 220
kΩ, resistor 20 is 15 kΩ, resistor 22 is 130 kΩ, resistor 28 is 1 kΩ, resistor 30 is 10 kΩ, resistor 32 is 12
kΩ, and the voltage on the bias power supply line 15 is 15 volts. Further, the emitter current negative feedback resistor 18 is semi-fixed in a finely adjusted state so that the third harmonic distortion rate is −9 μP or less in the maximum output and maximum distortion state. In the circuit as described above, the bias collector current of the transistor 12 is connected to the transistor type diode 21 and the resistor 22.
The current mirror circuit configured by
/R, is set.

However, Vcc is the voltage of the bias power supply line 15, and R is the value of the resistor 20. Further, the gain of the second stage amplifier circuit including the differential amplifier 25 is given by (R, +Ry)/R. However, R is the value of the resistor 36 and Ry is the value of the resistor 28. Therefore, if the maximum value of the resistor 30 is RxM, then 1 times ~ (
The gain can be changed within the range of RxMfRy)/R. The gain of the entire amplifier is determined by R of the resistor 14 as described above.
s and R of the resistor 32, and becomes approximately R and /Rs regardless of the gain of the second stage variable gain amplifier circuit.

Furthermore, if the resistor 19 is sufficiently large, the input resistance is the sum of Rs and a slight variation q that varies slightly depending on the gain of the second stage, and can be considered to be approximately constant. When a low frequency small signal is input to the input terminal 11 in the circuit shown in FIG.
It is given to the base of 2.

At this time, a pre-distortion characteristic is imparted by the function of the circuit consisting of the transistor-type diode 21 and the resistor 22. The first stage output having predistortion characteristics obtained from the collector of the transistor 12 becomes an input to a differential amplifier 25 via a coupling capacitor 23. In the second stage including the differential amplifier 25, a signal with desired second harmonic distortion is obtained by changing the value of the variable feedback resistor 30, and the signal is output to the output terminal 34 via the coupling capacitor 33.
sent to. At this time, the third harmonic distortion rate is kept suppressed, and the gain of the entire amplifier circuit is also kept substantially constant. Fig. 6 shows the circuit of Fig. 5 with a gain of 0 dB, that is, Rs=
R, and apply a 2Vrms input signal, and Rx
The results of frequency analysis are shown when changing the resistance to 0Ω, Ω, and 10kΩ.

As is clear from this characteristic diagram, the frequency F. The fundamental wave a remains almost constant even if Rx is changed. Also frequency 3
The third harmonic c of f0 is also kept below -9B almost regardless of the change in Rx. In this way, the second harmonic of the frequency disturbance changes in response to the change in R, as shown by B, , h, and b3. That is, when Rx=0, it becomes h, and when Rx=3kΩ, it becomes B. Therefore, when Rx=10kΩ, it is true. Therefore, it is possible to change the second harmonic distortion rate by 35 dB while keeping the overall gain substantially constant and suppressing the third harmonic distortion rate. FIG. 7 shows the circuit of FIG. 5 designed to have a gain of 0 dB, and the second harmonic distortion with respect to changes in the input signal voltage being determined.

However, the kite has the characteristic of Rx=0, the kite has the characteristic of R=3kΩ,
The wire exhibits a characteristic of Rx=10 kΩ. As is clear from this characteristic diagram, the second harmonic distortion rate can be changed by changing R, no matter what the input signal voltage is. As is clear from the above, according to the circuit shown in FIG. 5, the gain of the analog amplifier circuit is kept constant and the 53rd harmonic distortion rate is always suppressed to -9■P or less, while the 2nd harmonic distortion rate is reduced. can be controlled continuously.

Furthermore, the second harmonic distortion rate can be controlled by adjusting only one resistor 30, which simplifies the circuit configuration and adjustment.

Therefore, when adjusting sound quality, etc., by using the resistor 30 as a volume control and adjusting only one resistor, only the second harmonic can be suppressed while keeping the gain constant and suppressing the third harmonic. This is convenient because it allows you to change the settings and add thickness to the sound. Furthermore, since the transistor 12 and the transistor-type diode 21 are thermally coupled, it is possible to obtain distortion characteristics that are almost unaffected by changes in ambient temperature.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment and can be further modified.

For example, the transistor 12 and the diode 21 may be of PNP type. Further, in the embodiment, the resistor 30 is configured to be able to be adjusted from the outside at all times, but it may be configured to be semi-fixed after adjustment. Also, the differential amplifier 25 is
The resistor 28 may be a variable resistor in order to change the gain, ie, the second harmonic distortion rate, of the included second stage amplifier circuit. It can also be applied to things other than sound quality adjustment.

[Brief explanation of the drawing]

Figures 1, 2 and 3 are block diagrams showing conventional harmonic distortion rate control circuits, and Figure 4 is a block diagram showing conventional harmonic distortion rate control circuits. A graph showing the relationship between the second harmonic distortion rate and the third harmonic distortion rate when the necessary negative feedback is not applied, and FIG. 5 shows a second harmonic continuously variable circuit according to an embodiment of the present invention. 6 is an analysis diagram of the output frequency of the circuit shown in FIG. 5, and FIG. 7 is a graph showing changes in the second harmonic distortion rate when the input signal voltage is changed in the circuit shown in FIG. 5. In the symbols used in the drawings, 11 is a signal input terminal, 12 is a transistor, 14 is an input series resistor, and 15 is a signal input terminal.
is one bias power supply line, 16 is an output resistor, 17 is a ground line (the other bias power supply line), 13 is an emitter current negative feedback resistor, 20 is a bias resistor, 21 is a transistor diode, 22 is a resistor, and 25 is a differential dynamic amplifier, 26 and 27 are input terminals, 28 is a feedback setting resistor, 29
is the output terminal, 30 is the differential amplifier feedback resistor (variable resistor),
32 is a feedback resistor for gain setting.

Claims (1)

[Claims] 1 Input resistor 1 connected in series to analog signal input terminal
4, a transistor 12 whose base is connected to the input resistor 14, an output resistor 16 connected between the collector of the transistor 12 and one bias power supply line 15, and an emitter of the transistor 12 and the other bias an emitter current negative feedback resistor 18 connected between the power supply line 17; a bias resistor 20 connected between the base of the transistor 12 and the one bias power supply line; and a bias resistor 20 whose collector and base are connected to the transistor 1.
2, an emitter connected to the other bias power supply line 17 via a resistor 22, and thermally coupled to the transistor 12; and one input terminal 26 connected to the transistor 12. a differential amplifier 25 with a small harmonic distortion rate connected to the collector of the differential amplifier 25, and the other input terminal 2 of the differential amplifier 25.
7 and the other bias power supply line 17, and a fixed or variable feedback setting resistor 28 connected between the output terminal 29 of the differential amplifier 25 and the other input terminal 27. Variable or fixed differential amplifier feedback resistor 30
and a gain setting feedback resistor 32 connected between the output terminal 29 of the differential amplifier 25 and the base of the transistor 12; A second harmonic continuously variable circuit configured to change second harmonic distortion by adjusting a resistor 28.