JPH026244B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a waveform shaping circuit, and more particularly to a linear-sine wave conversion circuit that converts a triangular wave input signal into a sine wave output signal.

Function generators that generate various waveforms such as triangular waves, square waves, and sine waves with variable frequencies are widely used in operation tests of electronic equipment and communication equipment, biological physics experiments, etc. It is common to generate various waveforms such as rectangular waves and sine waves.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, prior art and embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows one of the function generators to which the present invention is applied.
FIG. 2 is a simple block diagram illustrating an example. The triangular wave generator 10 is comprised of a variable current source, a variable current sink, a timing capacitor, and a switching circuit (none of which are shown). The triangular wave is derived from an output terminal 13a directly connected to the triangular wave generator 10 (in some cases via a buffer amplifier). The triangular wave output of the triangular wave generator 10 is applied to a direct to sine wave conversion circuit (hereinafter referred to as a sine wave shaper) 11 and a comparator (or Schmitt circuit) 12. A sine wave is generated from the output terminal 13b connected to the sine wave shaper 11, and a sine wave is generated from the output terminal 13c connected to the comparator 12.
A rectangular wave (or square wave) is generated from.

FIG. 2 is a circuit diagram of a conventional sine wave shaper. The sine wave shaper consists of an input resistor 15 and a pair of diode/resistor networks 22 and 23 connected between input terminal 14 and output terminal 16. Although not shown, input terminal 1
4 is connected to the output terminal of the triangular wave generator 10 in FIG. The diode/resistance network 22 operates on the positive side of the input waveform and is an NPN transistor (hereinafter referred to as
transistor (TR) 17, potentiometer 18 that controls the base voltage of TR 17, diodes 19a to 19e, voltage dividing resistors 20a to 20
Consists of e. On the other hand, the diode/resistance network 23
operates on the negative side of the input waveform, and the polarity of TR17' and diodes 19'a to 19'e is the same as that of network 22.
The structure is in contrast to the circuit network 22, except that the TR and the diode are different. That is, potentiometer 18' and resistors 20'a-2 of network 23
0'e are potentiometers 1 of network 22, respectively.
8 and resistors 20a to 20e. By the way, the common contact of the first diodes 19a, 19'a is directly connected to the output terminal 16, but the diodes 19b-19'b, 19c-19'c, 19d-1
The common contacts of 9'd and 19e-19'e are resistors 21b, 21c, and 2, which have larger resistance values in the order of codes.
It is connected to 1d and 21e.

The input resistor 15, the resistors 21b to 21e, and the resistors 20a to 20e constitute a variable attenuator that attenuates the triangular wave input signal at different attenuation ratios as the input signal becomes larger, and the diodes 19e to 20e
The cathode voltage of 19a increases in this order.
Each cathode voltage is determined by the base voltage of the TR 17 set by the potentiometer 18 and the resistance values of the resistors 20a to 20e. The above also applies to the circuit network 23, although the polarity of the voltage is reversed.

Now, the operation of the circuit shown in FIG. 2 will be explained with respect to the circuit network 22. If the input signal is very small, all diodes 19a-19e are off and the input signal appears at the output 16 with minimal attenuation. When the input signal level reaches the cathode voltage of diode 19e, diode 19e is turned on and the attenuation ratio increases. When the input signal level further increases, the diodes 19d, 19c, . . . turn on in this order, and the attenuation ratio further increases. Therefore, if the resistance values of the resistors 21b to 21e are appropriately selected,
It is possible to convert a triangular input signal waveform to a sine wave.

FIG. 3 is a circuit diagram showing an outline of another conventional sine wave shaper. This sine wave shaper consists of resistor 2
The circuit comprises four diode bridges 27a to 27d connected in parallel to the input terminal 24 via 5, an operational amplifier 31 having input/output resistors 32 and 33 and connected to the output terminal 26, and the like. bridge 2
the resistance values of resistors 28 and 29 (shown only for bridge 27a for simplicity) connected to 7a to 27d and acting as current source and current sink, respectively;
By appropriately selecting the resistance values of the variable resistors 30a-30d, the current can be controlled at different levels of the input signal. Therefore, a triangular wave input signal can be converted into a sine wave signal.

By the way, the conventional sine wave shaper described above has a large number of parts and a complicated circuit configuration, and requires troublesome adjustment in order to minimize sine wave distortion.
More importantly, the use of a large number of passive components precludes operation at high frequencies.

Therefore, an object of the present invention is to provide a sine wave shaper, that is, a waveform shaping circuit, which has a small number of parts, a simple circuit configuration, and operates accurately over a wide frequency range.

Embodiments of the first invention of the present application will be described below with reference to FIGS. 4 to 6. FIG. 4 is a basic circuit diagram of the present invention. The principle of the invention is that the trigonometric function sin
It is based on the point that (KX) can be approximated by the following equation (1) (A and B are constants).

sin(KX)(AX−BX ³ )/(1+X ² ) (1) According to the present invention, equation (1) can be constructed using a circuit with a small number of parts and easy adjustment. The present invention utilizes the so-called Gilbert multiplier technology proposed by Barry Gilbert and disclosed in Japanese Patent Publication No. 48-20932 (the patentee is the present applicant). In FIG. 4, complementary input signal currents Iin ¹ and Iin ² are connected to diode-connected TRs (D ₁ ,
D ₃ ) and (D ₂ , D ₄ ) and are summed at a common connection point 12 where appropriate voltages are applied.
The voltage drops of TR (D ₁ , D ₃ ) and (D ₂ , D ₄ ) are
Each is applied to the bases of a differential TR pair (Q ₁ , Q ₂ ) whose emitters are connected to a current source I ₂ to control this differential TR pair. On the other hand, the voltage drops at TRD ₃ and D _{4 are}
applied to the bases of the TR pair (Q ₃ , Q ₄ ), this differential
Control TR pairs. The collectors of the differential TR pair (Q ₁ , Q ₂ ) are cross-connected to the collectors of the differential TR pair (Q ₃ , Q ₄ ), respectively, and a pair of output terminals 13 and 14 are connected to each other.
is connected to.

By the way, the base-emitter voltage V _BE of the bipolar TR can be accurately expressed by the following equation (2).

V _BE =kt/qLn(I _C /I _S )...(2) Where, k: Boltzmann's constant t: Absolute temperature q: Electron charge I _S : Saturation current of TR I _C : Collector current Now, TR D ₃ , Q ₃ , Q ₄ and D ⁴ , the following equation (3) holds true for the closed lube regarding the base emitter.

V _D3 −V _BE3 +V _BE4 −V _D4 =0 (3) Here, V _D3 , V _BE3 , V _BE4 and V _D4 are respectively,
This is the base-emitter voltage of TRD ₃ , Q ₃ , Q ₄ and D ₄ . Since the saturation currents of TR D ₃ and D ₄ and TRQ ₃ and Q ₄ are equal (I _SD and I _ST , respectively), the second and
The following equation (4) can be found from equation (3).

kt／q{LnI _D3 ／I _SD −LnI _C3 ／I _ST ＋LnI _C4 ／I _ST −LnI _D4 ／I _SD }=kt／qLnI _D3 ／I _SD・I _C4 ／I _ST I _D4 ／I
_SD・I _C3 /I _ST =0(4) Therefore, I _D3 /I _D4 =I _C3 /I _C4 ...(5). Since the currents flowing through TR _D3 and _D4 are complementary to each other, I _D3 and I _D4 can be set to (1+X/2)Iin and (1-X/2)Iin, respectively (however, Iin = Iin ₁ + Iin ₂ ).

Therefore, I _{C3 /I C4 = 1 +}

I _C3 = (1 + X / 2 _{) I 1} ... ( ₇ ) I _C4 = ( _{1 -} Regarding the closed loop including , the following relational expression (9) also holds true.

V _D3 +V _D1 −V _BE1 +V _BE2 −V _D2 −V _D4 =0 (9) Similarly to when formula (4) is derived, kt/qLnI _C2 /I _ST・I _D1 /I _SD・I _D3 /I _SD /I _C1
/I _ST・I _D2 /I _SD・I _D4 /I _SD = 0…(10) Therefore, I _C1 /I _C2 = I _D1 I _D3 /I _D2 I _D4 = (I _D1 /I _D2 ) ² = (
1+X) ² /(1-X) ² (11) By the way, since I _C1 + I _C2 = I ₂ (12), equations (11) and (12) become as follows.

I _C1 = (1 + X) ² / 2 (1 + X ² ) I ₂ ... (13) I _C2 = (1 - X ^{) 2} / ₂ (1 + The output currents Iout ₁ and Iout ₂ respectively flowing in are: Iout ₁ = I _C1 + I _C4 = (1 + X) ² I ₂ + (1-X) (1 + X ² ) I ₁ /2 (
₁ +X ² ) …(15) Iout ₂ = I _C2 + I _C3 = ⁽ 1-X) 2 I ² + ( _1+
1 ⁺ _{_}
( ^2I ₂ −I ₁ ) _X ⁻ I 1
It can be seen that Iout is a sine wave function. Furthermore, (17)
(2I ₂ −I ₁ ) and I ₁ in the numerator of the formula are each the constant A of the formula (1)
and B. Therefore, a sine wave output can be obtained by the circuit of FIG. 4 by simply adjusting the current sources and appropriately setting the currents I ₁ and I ₂ .

FIG. 5 shows an example in which the circuit shown in FIG. 4 is actually applied. Differential amplifier or voltage-current converter 11
5 receives a single-ended or push-pull triangular wave input signal voltage and supplies complementary triangular wave currents Iin 1 and 11 to input terminals 10 and 11 of a converter 116, which corresponds to the sine wave converter shown in _FIG.
Apply Iin ₂ . The triangular wave currents Iin ₁ and Iin ₂ are added at the connection point 12 and connected in series with the diode 11.
7 and resistor 118 . The voltage at connection point 12 is determined by TR 119, which has emitter resistors 121 and 122, respectively, and acts as constant current sources I ₁ and I ₂ .
and 120 bases. diode 1
Reference numeral 17 is for temperature compensation of the base-emitter voltage V _BE of each of the TRs 119 and 120, and a sinusoidal output current is derived from the output terminals 13 and 14.
Note that it is clear that the differential amplifier 115 can be omitted if the complementary triangular wave currents are obtained directly from the input signal source.

FIG. 6 is a circuit diagram showing an embodiment of the second invention of the present application, and for simplicity, the same parts as in FIG. 4 are given the same reference numerals. Part 12 surrounded by a dashed line
3 is the main part of this embodiment, which includes a differential TR pair (Q' ₁ , Q' ₂ ), a diode-connected TR pair (D' ₁ , D' ₂ ),
It consists of another differential TR pair (Q' ₃ , Q' ₄ ) whose base-emitter junctions are connected in series with TR D' ₁ and TR D' ₂ , respectively. The collectors of TR Q' ₁ and Q' ₄ are connected to the output terminal 14', and the collectors of TR Q' ₂ and Q' ₃ are connected to the other output terminal 13'.

Input differential amplifier 124 includes a pair of TRs Q ₅ and Q ₆
and a current source _I1 , and based on a triangular wave input signal applied to input terminal 125, terminals 10' and 1
Currents Iin ₁ and Iin ₂ are drawn from 1'.

By the way, regarding the current flowing through TR Q′ ₃ , D′ ₂ and TR Q′ ₄ , D′ ₁ , the following equation holds true.

I _D ′ ₁ = I _C ′ ₄ = Iin ₂ … (18) I _D ′ ₂ = I _C ′ ₃ = Iin ₁ … (19) Iin ₁ + Iin ₂ = I ₁ … (20) Here, Iin ₁ = 1 −X/2I ₁ , Iin ₂ =1+X/2I ₁ .

Now, the base-emitter junctions of TR Q′ ₁ to Q′ ₄ , D′ ₁ , and D′ ₂ form a closed loop, so V _BE3 +V _D2 +V _BE2 −V _BE4 −V _D1 −V _BE1 =0 (21 ) Therefore, I _C ′ ₂ /I _C ′ ₁ = I _D ′ ₁ I _C ′ ₄ /I _D ′ ₂ I _C ′ ₃ = (
^{1 +} _{_ _} ^{_ _} _{_}
) I _C ′ ₂ = (1+X) ² /2 (1+X ² ) I ₂ …(24
) (18), (19), (23) and (24) are converted into (7), (8),
Comparing equations (13) and (14), it can be seen that the circuit in FIG. 6 operates exactly the same as the circuit in FIG. 4. Therefore, the sine wave output current is output to the output terminal 1.
3' and 14'.

As explained above, the invention of the present application has a much simpler configuration than conventional waveform shaping circuits. Furthermore, the input impedance is low, and since it is composed only of TRs and does not include passive elements, it operates well from low frequencies to high frequencies of, for example, 100 MHz or higher. Therefore, a sine wave shaper with a wide bandwidth can be obtained. Note that the accuracy of the sine wave output waveform obtained in the embodiment of the present invention is a maximum error of about 0.4% over a wide frequency range.

Although the embodiments of the present invention have been described above, modifications and changes to the embodiments will be obvious to those skilled in the art.

[Brief explanation of drawings]

Figure 1 is a block diagram of a typical function generator to which the invention of the present application is applied, Figures 2 and 3 are respectively conventional sine wave shaping circuits, and Figure 4 is a basic circuit of the first invention of the present application. FIG. 5 is a block diagram showing a case where the circuit of FIG. 4 is actually used, and FIG. 6 is a circuit diagram of an embodiment of the second invention of the present application. (Q ₃ , Q ₄ ) and (Q′ ₁ , Q′ ₂ ) are the first transistor pair, (D ₃ , D ₄ ) and (D′ ₁ , D′ ₂ ) are the second transistor pair, ( D ₁ , D ₂ ) and (Q′ ₃ ,
Q′ ₄ ) are the third transistor pair, Q ₁ and Q ₂ are the fourth transistor pair, respectively.
Transistor pair I ₁ and I ₂ are current sources.

Claims (1)

[Claims] 1. A first pair of transistors whose common emitters are connected to a first current source, and whose bases and collectors are interconnected to form a diode connection, and whose interconnected bases and collectors are connected to the bases of the first transistor pair. A second pair of transistors each having a common emitter connected to a reference potential source, a pair of input terminals into which triangular wave currents having a complementary relationship are respectively input, and a diode connection with their respective bases and collectors interconnected. and a third pair of transistors connected between the input terminal and the second pair of transistors, each having its base connected to the mutually connected base and collector of the third pair of transistors, and having a common emitter connected to a second current source. a fourth transistor pair, wherein the collectors of the first and fourth transistor pairs are connected to a pair of output terminals across each other. 2 A first pair of transistors whose common emitters are connected to the first current source; and a second pair of transistors whose bases and collectors are interconnected to form a diode connection, and whose emitters are connected to the bases of the first pair of transistors; a third pair of transistors whose bases are connected to a reference potential source and whose emitters are connected to the interconnected bases and collectors of the second pair of transistors; and the current from the second current source is divided into triangular wave currents having a complementary relationship. , further comprising an input means for inputting the triangular wave current to the second and third transistor pairs connected in series, and the collectors of the first and third transistor pairs are respectively connected to the pair of output terminals. waveform shaping circuit.