JPH0319531A - Unbalance/balance conversion circuit - Google Patents

Abstract

PURPOSE:To efficiently output the output of an amplifier to a balance line by adjusting the level of an input signal from an unbalance line with a level adjustment section, supplying the result to a matching adjustment section and reducing the output signal of the amplifier lost with a matching resistor. CONSTITUTION:A level adjustment section 3 adjusts the level of an input signal Vi from an unbalance line to change a transmission level to a matching adjustment section 1 comprising series circuits 11, 12 consisting of two systems of amplifiers 111, 112 and output resistors 112, 122 having a feedback circuit 2 from an output terminal. The matching adjustment section 1 is constituted of amplifiers 111, 121 having the two series circuits and being inverting amplifiers with a prescribed voltage gain A1 of two series connected in parallel and the output resistors 112, 122 and the feedback circuit 2 feeds back each output v0 of the series circuits 11, 12 of the matching adjustment section 1 to a noninverting input terminal + of the amplifiers 111, 121 respectively. The series circuits 11, 12 composed of the amplifiers 111, 121 and the output resistor RF apply the matching adjustment of the impedance matching with a post-stage balance line. Then the output of the amplifier is outputted efficiently to the balance line.

Description

[Detailed Description of the Invention] [Summary] An unbalanced/balanced conversion circuit that uses an amplifier to amplify a signal input from an unbalanced line that is unbalanced with respect to the ground, performs impedance matching, and outputs the signal to a balanced line that is balanced with respect to the ground. Regarding this, reduce the loss of the amplifier output signal due to the impedance matching resistor,
The aim is to create an unbalanced/balanced conversion circuit that is convenient for use and can efficiently output the output of an amplifier to a balanced line.The purpose is to create an unbalanced/balanced conversion circuit that can efficiently output the output of an amplifier to a balanced line.The circuit is designed to invert and differentially amplify the signal ν1 input from an unbalanced line with a constant voltage gain. It consists of a series circuit of an amplifier and its output resistor R, and a matching adjustment section that adjusts impedance matching with the balanced line, and each output ν of the series circuit. A feedback circuit that feeds back the signal Vi to the non-inverting input terminal of each amplifier, and a level adjustment unit that adjusts the level of the input signal Vi and changes the output level are provided in the front stage of the two series of amplifiers, and the level adjustment unit After adjusting the level of the human input signal Vi from the unbalanced line by the section, it is supplied to a matching adjustment section that connects two series of amplifiers with feedback circuits and an output resistor in series, and the output signal of the amplifier is compensated for by the loss in the matching resistor. The output of the amplifier should be reduced and outputted efficiently to the balanced line.

[Industrial application field]

The present invention relates to a transmission format conversion circuit, and more particularly to an unbalanced/balanced conversion circuit that converts a human-powered signal from an unbalanced line that is unbalanced with respect to the ground to a balanced line that is balanced with respect to the ground, and outputs the signal after manoching the impedance. .

? [Prior art] As shown in Fig. 3, a conventional unbalanced/balanced conversion circuit inverts and amplifies a signal V8, which is manually inputted from an unbalanced line with respect to the ground E, with a constant voltage gain A, in parallel. Two series of operational amplifiers (A1) l1lA, 121A and their output resistance (RF) 11■A1]2■. The output terminals of the series circuits are connected to both ends of a balanced line balanced with respect to the ground ε, and the connections between the both ends and the ground are terminated by resistors 21A and 22A. Then, the impedance matching with the balance line in the subsequent stage is adjusted by the resistor RF of the output of each amplifier, and each output voltage ν0 of each series circuit is applied to each of the resistors 21A and 22A between the ground E of the balance line and both ends. The structure is such that it is applied. (Problem to be Solved by the Invention) Since the conventional unbalanced/balanced conversion circuit has the above-mentioned configuration, when matching the impedance with the balanced line in the latter stage using, for example, an impedance of 600Ω, Since the output impedance of the operational amplifier is substantially zero, the value of the resistor R for matching adjustment on the output side of each operational amplifier is selected to be 300Ω.Therefore, each voltage v0 across the resistors 21A and 22A of the balanced line is The voltage becomes V■/2, which is half of the output voltage ν■.

In other words, there is a problem that only half of the output voltage V of the amplifier can be output to the balanced line, resulting in poor efficiency. SUMMARY OF THE INVENTION An object of the present invention is to provide an unbalanced/eight-lance conversion circuit that reduces the loss of the output signal of an amplifier due to a matching resistor and efficiently outputs the output of the amplifier to a balanced line.

? Means for Solving the Problem) This problem is solved by the input signal V. from the unbalanced line as shown in FIG. Two parallel series amplifiers 11I, 12. and its output resistance 1I,
, 12 series circuits 1112 for adjusting impedance matching with the balanced line. Adjustment section (1
), a feedback circuit (2) that feeds back each output v0 of the series circuit IL12 to the non-inverting input terminal of each amplifier 11I, 12, and an input signal ν. A level adjustment section (3) is provided to adjust the level of the amplifiers 11I, 121 and change the output level, thereby reducing the loss of the output signals of the amplifiers 11I, 121 at the matching resistor Rr, and adding amplifiers 1I, , 121 to the balanced line. 12. This problem is solved by the present invention, which is configured to output the output efficiently.

In the principle diagram shown in FIG. 1 showing the basic configuration of the unbalanced/balanced conversion circuit of the present invention, 1 is a matching adjustment section that adjusts impedance matching with the balanced line, and the matching adjustment section 1 adjusts the input signal Vl from the unbalanced line. Two series of parallel amplifiers 1I, . . . perform inverted differential amplification with a constant voltage gain A. 12, and its output resistance 11
■． 12■ series circuit 1I, . Consists of 12.

2 connects each output v0 of the series circuits 1I, 12 of the matching adjustment section 1 to the respective amplifiers 11I, 12. This is a feedback circuit that feeds back to the non-inverting input terminal of

3 is two series of amplifiers 11I, 1 of the matching adjustment section l.
2. A level adjustment section for obtaining a constant ratio A3 of output voltage and input voltage, which is provided at the front stage of the input voltage, adjusts the level of input signal Bv8 from the unbalanced line to output voltage νi A3.
is sent to two series of amplifiers 11l and 12I.

? Operation] The level adjustment section 3 of the present invention receives the input signal ν from the Anhara line. A two-series amplifier 11I that adjusts the level of and has a feedback circuit 2 from the output end,! 2, and its output resistance 11
■． 12 ■ series circuit II, 12 matching adjustment section l
change the output level.

The masoching adjustment section l has two series of constant voltage gain A in parallel.
Two series circuits 1I, 1 consisting of amplifiers 11l, 12l, which are inverting differential amplifiers of 1, and their output resistors 11■, 12t.
2, the feedback circuit 2 connects each output v0 of the series circuit IL 12 of the matching adjustment section 1 to amplifiers 111 and 1, respectively.
It is fed back to the non-inverting input terminal + of 2. and amplifier 11
I, 12. and its output resistance R, a series circuit 11,I,
2 is the impedance with the Harans line in the latter stage? Adjust munching for consistency.

In FIG. 1, if the overall impedance of the balance line in the latter stage is Z, the impedance between the ground E and each end is Z/2 (Ω), and the voltage across the impedance Z/2 is the voltage ν. Therefore, the current 10 flowing into the impedance Z/2 is expressed by the following equation, i. ■ vo/(Z/2)・(VO VOA
I)/RF-(1) is established, the unbalanced structure of the present invention
This means that the balanced conversion circuit is matched with the balance line at the subsequent stage in terms of impedance Z (Ω).

Also, the voltage ν between the ground E and each end of the balanced line. teeth,
From the figure, if the ratio of the output voltage and input voltage of the level adjustment section 3 is A3, the input voltage to each amplifier is (A3v H
+ vo), and its output voltage ν4. Since the voltage gain of each amplifier is ^1, (A3v8+v.) becomes A. The current flowing from each amplifier to the impedance Z/2 via the output resistor RF is (A3νi + vo)
A+ / ((Z/2)+R r ), so
Voltage ν across impedance Z/2. is vo= (Z/2) (A3v; +νO)A, /
((Z/2 + R F ). Transforming the above formula, ν.・νi (Z/2)A, A./ (( 7, /2)
+ R r −A, Z/2) (2), and further from (1), RF・(Z/2)(1 − A,), A.・1-
(R, /(Z/2))(3) Substitute (3) into (2), ν.・νi ((Z/2)-1t F ) A3/
2RF (4), and by changing the voltage ratio A3 between the output of the balance adjustment circuit 3 and the human power, the tangent f[j! E and the voltage ν between each end. can be determined.

Moreover, the voltage ν. and the output voltage vA+ of the amplifier is ν.・νAl − Z/2/(Z/2+Ib) is established.

In the conventional circuit, RF=Z/2, so ν.・V Al/
However, in the present invention, if R p<7,/2, 1/2<Z/2/(Z/2
+llr ) < 1, and the output voltage of the amplifier is more efficiently output to the Harance circuit, and the problem is solved.

? Embodiment] FIG. 2 is a circuit diagram showing the configuration of an unbalanced/balanced conversion circuit according to an embodiment of the present invention, in which matching with the eight-lance line in the latter stage is performed by munching with impedance Z of 600Ω as in the conventional example. This is an example of a case where The matching adjustment unit 1 of the present invention includes an amplifier A. and gain A
．． =27k,/. 3ok. o. It consists of a series circuit 1I, 12 of an amplifier A1■ of 9 and a resistor R of each output, and assuming that the resistor R is 30Ω, both operational amplifiers ^lI. Each output voltage νAI of AI2
I+ V^12 and the voltage across each impedance Z/2 between the ground E of the balanced line and both ends v0VOZ
The relationship between νo”νa1( Z/2) / (( Z/2)+RF
]2ν■300/ (300+30) = 0.909ν. Both can be converted efficiently.

Also, the human power voltage V. from the unbalanced line. and level adjustment section 3
The output to input voltage ratio A, and the output voltage ν to the ground E and both ends of the Harance line. The relationship with is ν.・νs ((Z
/2)-RF) A3/2RF・νr (30
0-30) A3/2X30・4.5 Vi Aff, and the voltage ratio A3 of the level adjustment section 3 is ^,・270
/(1100+270)・0.197, so ν.・0.891ν.

[Effects of the Invention] As explained above, according to the unbalanced/balanced conversion circuit of the present invention, it is possible to match the impedance with the balanced line in the subsequent stage, and to reduce the loss due to the matching resistor of the output signal of the amplifier. Since the output of the amplifier can be efficiently output to the balanced line, even if this circuit is constructed using the same components as the conventional circuit, it can output a level higher than the maximum output level of the conventional circuit. Therefore, the effects of reducing the cost and improving the convenience of use of the unbalanced/balanced conversion circuit can be obtained.

[Brief explanation of the drawing]

Figure 1 is a principle diagram showing the basic structure of the unbalanced/balanced conversion circuit of the present invention, Figure 2 is a circuit diagram showing the configuration of the Andhara/Harance conversion circuit of the embodiment of the present invention, and Figure 3 is the conventional unbalanced conversion circuit. - It is a block diagram of a balance conversion circuit. In the figure, l is a matching adjustment section, 2 is a feedback circuit, 3 is a level adjustment section, I, 1, . 12. is Anbu, 11 ■. 12■ is an output resistance.

Claims (1)

[Claims] In an unbalanced/balanced conversion circuit that matches an impedance of a signal input from an unbalanced line that is unbalanced with respect to the ground and outputs it to a balanced balanced line, an input signal (V_i) from the unbalanced line Two series of parallel amplifiers (11_I
, 12_I) and its output resistance (11_Z, 12_Z)
A matching adjustment section (1) that adjusts the impedance matching with the balanced line, which consists of a series circuit (11, 12) of
and each output (V_O) of the series circuit is connected to an amplifier (11
A feedback circuit (2) that feeds back to the non-inverting input terminal (+) of the two series of amplifiers (_I, 12_I), and a feedback circuit (2) that feeds back the input signal (
One level adjustment section (3) is provided to adjust the level of the input signal (V_i) and change the output level, and after the level adjustment section (3) adjusts the level of the input signal (V_i) from the unbalanced line, the feedback circuit ( 2) is supplied to the matching adjustment section (1) of a series circuit of two series of amplifiers (11_I, 12_I) and output resistors (11_Z, 12_Z), reducing the loss of the output signal of the amplifiers (11_I, 12_I) and improving efficiency. An unbalanced/balanced conversion circuit characterized by good output to a balanced line.