HU206005B - Circuit arrangement for power amplifying voice frequency signals in receiving path of the transmission-type equipments - Google Patents

Abstract

Field of the Invention The present invention relates to a switching arrangement for amplifying the power of signaling frequency signals of transmission technology equipment having a bias distributor or voltage generating unit (1) having a control input (11). Carrying voltage (half of the supply voltage of the new and one voltage source (1/2 U) to the control input (11) of the bias distributor or voltage generator (1)), the first output (12) of the fourth input (26) of the demodulator (2) , its second output (13) is connected to the third input (25) of the demodulator (2), the modulating voltage (µm) modulating to the first and second inputs (21,22) of the demodulator (2). 24) second and first inputs (32, 31) of the filter circuit (3), the first output (33) of the filter circuit (3) to one arm of the first capacitor (Cl), second u 0 «Figure 4 EN 206 005 BA description : 8 pages (including 2 tabs)

Description

The two terminals of the secondary winding of the output transformer (TI) form the output (u _off ) of the switching arrangement. The switching arrangement is characterized in that one arm of the second capacitor (C2) feedback to the other end of the fourth resistor (R4) is connected to one arm of the third capacitor (C3) and the other arm of the second capacitor (C2) and one end of the fifth resistor (R5). . The other armature of the third capacitor (C3) to the other terminal of the primary transformer (TI) winding, the other end of the fifth resistor (R5) to ground, the half voltage of the single-voltage voltage source (1) of the biasing or voltage generating unit (1) .) equivalent to the output bias voltage (U _E) producing hannadik (14) connected to the first and second resistors (Ri, R2) connected to the other end (Figure 4).

BACKGROUND OF THE INVENTION The present invention relates to a circuit arrangement for amplifying the power of the received audio frequency signals of transmission equipment, preferably controlled by a low level audio signal recovered by the detnodulator or demultiplexer from the multiplexer signal to provide a power level signal at the output of the circuitry.

A wide variety of circuitry for power amplification is known in the art.

The state-of-the-art amplifier widely used in Ericsson's well-known 12-channel overhead line system is made up of discrete semiconductor elements (transistors, diodes), transformers, resistors, and capacitors. High-voltage cooling electrolytic capacitors are used for direct current separation and sonic "cooling". The output impedance is set to the desired value with serial resistance.

The disadvantage of this solution is that the electrolytic capacitors are expensive on the one hand and large on the other hand and are therefore not suitable for an integrated design. A further disadvantage is that the series resistor connected in series with the primary winding of the transformer consumes half of the output power and therefore requires double output and power output from the active circuit. As a result, efficiency is degraded and distortion is greater.

Another known solution is the 128 kHz system of Tesla, whose power amplifier also loses half of the output power at the resistor connected in series with the primary winding of the transformer, which is a disadvantage of this solution.

Also known in the Fairchild catalog (Fairchild Book One, The Complette Linear Book, p. 482) is an embodiment of an operational amplifier circuit. The connection is simple, it can be built and integrated with few elements.

The disadvantage of this solution is that it has a limited usability because it requires two power supplies, one positive and one negative U ₊ , U. which is often not available to users in applications.

To solve this problem, Fairchild, also in this catalog (p. 482), recommends a circuit that already supplies power with a single negative U. voltage source. The disadvantage of this solution, however, is that the realization of the negative U. voltage source (-24 V) requires a high-value (300 uF, 15 V) cooling capacitor, which is expensive on the one hand and cannot be integrated due to its large size. A further disadvantage is that high output inductance of the output transformer is required to produce the output impedance at the required exact value, i.e., good reflection damping, which results in increased loss due to either the use of a large transformer.

It is an object of the present invention to overcome the shortcomings of the prior art and to provide a state-of-the-art circuit arrangement

- constant amplification over a wide frequency range;

its output impedance is of the required value and accuracy, i.e. its reflection damping is sufficiently high relative to the nominal impedance40;

- it can be powered by a single voltage source (usually grounded on one branch);

- low power loss, ie good efficiency;

- small non-linear distortion;

- its structure is made of simple, small elements, integrated technology;

- its production is economical.

The present invention is based on the discovery that when a DC disconnecting capacitor is coupled to the output transformer primary winding coil circuit, and a feedback capacitor is applied to the current feedback branch, the DC input of the operation amplifier is inverting to the DC input of the operation amplifier. with half of the power required for a single-cell voltage source, a switching arrangement can be created in which both capacitors are low value, integrated and inexpensive, and the amplification is constant over a wide frequency range, since

The frequency dependent distribution of the DC voltage caused by the DC disconnecting capacitor can also be compensated by the frequency dependent feedback rate of the feedback capacitor, and the capacitive frequency dependent feedback is transformed by an output impedance such that allows the use of a low-loss output transformer with good reflection damping, with little non-linear distortion, using a single voltage source.

The invention thus relates to a circuit arrangement for amplifying the power of the received audio signals of transmission equipment having a biasing or voltage generating unit having a control input. Half of the supply voltage of the carrier voltage and single-pole voltage source to the control input of the biasing or voltage generating unit is the first output to the fourth input of the demodulator, the second output to the third input of the demodulator and the first and second inputs of the demodulator.

The first and second outputs of the demodulator are connected to the second and first inputs of the filter circuit, the first output of the filter circuit to one of the arms of the first capacitor, and the second output to ground. Another arm of the first capacitor is connected to the non-inverting input of the operational amplifier and to one end of the first resistor, the other end of the first resistor to the other end of the second resistor, one end of the second resistor to the inverting input of the operational amplifier.

The other end of the third resistor is connected to the output of the operation amplifier and to one of the output transformer primary windings, the unearthed branch of a single-core voltage braid to one voltage connection point of the operational amplifier and the single-point voltage source ground. The two terminals of the secondary winding of the output transformer are also the output of the circuit arrangement. The circuit arrangement is characterized in that one arm of the second capacitor feedback to the other end of the fourth resistor, the other arm of the second capacitor is connected to one arm of the third capacitor and one end of the fifth resistor. The other armature of the third capacitor for the other terminal of the primary winding of the output transformer, the other end of the fifth resistor to ground, the biasing voltage of the biasing or voltage generating unit to the first biasing voltage of the second biasing voltage; join.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention and the present invention will be described in more detail with reference to the drawings, which are as follows:

Figure 1 is an Ericsson amplifier used in a 12-channel overhead line system;

Figure 2 is a diagram of a Fairchild amplifier circuit with an operational amplifier and two voltage sources;

Figure 3 is a diagram of a Fairchild amplifier circuit with an operational amplifier and a single voltage source;

Figure 4 illustrates a circuit arrangement according to the invention.

Figure 1 shows an amplifier used by Ericsson in a 12-channel overhead line system consisting of discrete semiconductor elements, first, second (D1, D2) diodes and first, second, third (TR1, TR2, TR3) transistors and resistors and (T1A) is made of an output transformer. The amplifier contains many components, using high value first, second (C _H1 , C _H2 ) electrolytic capacitors for sound "cooling" and direct current isolation, which are not suitable for production in an integrated design. The output impedance is set to the desired value by a series resistor (R _s ) connected in series with the primary winding of the (TIA) output transformer, which consumes half of the output power, which requires twice the output power from the second, third (TR2, TR3) transistors which, in turn, degrades efficiency and increases distortion.

Figure 2 illustrates a Fairchild (Al) power amplifier circuit and two power amplifiers, one positive and one negative (U ₊ , U), which are simple to assemble and integrate with a small number of components. However, this switching is of limited use, since there are no two voltage sources available at most applications.

Figure 3 shows an amplifier circuit implemented by Fairchild (Al) with an operational amplifier and a single negative (U.) voltage source, which requires a high-value ( _CH ) cooling capacitor to realize the negative (U.) voltage source, which is expensive on the one hand cannot be integrated. On the other hand, in order to produce the output impedance to the specified exact value, i.e., good reflection damping, high inductance of the (T1C) output transformer is required, which results in either large transformer size or increased loss.

Fig. 4 shows a circuit arrangement according to the invention, which has a bias distribution or voltage generating unit (1) having a control input (11). To the control input (u _c ) of the biasing or voltage generating unit (1), the carrier voltage and the single-voltage voltage source (U.) half of the supply voltage (1/2 U.), the first (12) output (2) of the demodulator fourth (26). a second output (13) of the demodulator (2) is connected to a third output (25) of the demodulator (2) and a modulating voltage (u _m ) is applied to the first and second input (21, 22) of the demodulator (2). The first and second outputs (23, 24) of the demodulator (2) for the second, first inputs (32,31) of the filter circuit, the first (33) outputs of the filter circuit (3) for an armature of the first capacitor (Cl), its output is grounded. The other armature (4) of the first capacitor (Cl) to the non-inverting input of the operational amplifier (42) and

One end of the first resistor (R1) to the other end of the second resistor (R2), one end of the second resistor (R2) to the inverting input (41) of the operational amplifier (4), third and fourth (R3, R4) is connected to one end of a resistor. The other end of the third resistor (R3) to the output (44) of the operational amplifier (4) and one terminal of the primary winding of the output transformer (TI) to a voltage connection (43) of the operational amplifier (4) is unearthed. to the other voltage connection point (45) is connected to the single-point voltage source ground. The two terminals of the secondary winding of the (TI) output transformer are also the output (u _off ) of the switching arrangement. The switching arrangement is characterized in that one arm of the second capacitor (C2) which feeds back to the other end of the fourth resistor (R4) is located on one arm of the second capacitor (C2) and one arm of the third capacitor (C3) and one end of the fifth resistor (R5). connected. The other armature of the third capacitor (C3) for the other terminal of the primary winding of the output transformer (TI), the other end of the fifth resistor (R5) to ground, the biasing voltage or voltage generating unit (1) _The third output (14) of the biasing voltage (UE) is connected to the other end of the first and second resistors (R1, R2).

A preferred embodiment of the circuit arrangement according to the invention is characterized in that the bias voltage (Ug) is produced by means of a carrier voltage (u _c ) connected to the control input (11c) of the biasing or voltage generating unit (11).

The operation of the circuit arrangement according to the invention is as follows:

First and second connectors (21,22) to the input of the demodulator (2) (u ™) modulating the voltage (f _ra) per frequency fourth (26) input of the demodulator (2) through (1) the bias-voltage generating unit distributing or (u _c ) carrier voltage (f _c ) frequency. The frequency spectrum of the voltage at the first and second outputs (23, 24) of the demodulator (2) includes the frequencies f _m + f _c and f _m- f _c . Among these, the useful components of the frequency f _m -f _c are passed by the filter circuit (3), which is a low-pass filter, and suppressed by the components of the frequency f _m + f _c . The bias distribution or voltage generating unit (1) is configured such that the carrier voltage (u _c ) connected to the control input (11) and half the supply voltage (1/2 U.) of the single-source voltage source (U.) are alternating voltage and dc voltage. component voltage is supplied to the first (12) output of the first (12) and thus the fourth (26) of the demodulator (2), while the second (13) and thus the third (25) and third (14) of the demodulator (14). ), only the DC component of the voltage connected to the input of the controller (11), i.e. the voltage (1/2 U.), is displayed. The DC voltage appearing at the second and third outputs (13, 14) of the biasing distributor or voltage generating unit (1) provides a DC bias for the operation of the demodulator (2) and the operational amplifier (4). The first capacitor (Cl) performs direct current isolation. As a result of the operation of the biasing or voltage generating unit (1), the demodulator (2), the filter circuit (3) and the first capacitor (Cl), the first, second, third, fourth and a fifth (R1, R2, R3, R4, R5) resistor, second, third capacitor (C2, C3) capacitor and (TI) output transformer having both (41) inverting and (42) non-inverting inputs close to direct current (1/2 U). ), while from an AC point of view the non-inverting input (42) is the input of the amplifier circuit and the inverting input (41) is the input for receiving the feedback signal. The dominance of the complex feedback system is the ratio of the voltage feedback defined by the second, third (R2, R3) divider and the dominantly the second, fourth, and fifth (R2, R4, R5) resistances, which sets the the output impedance of the amplifier circuit, and the sum of the voltage feedback and the current feedback the magnitude of the amplification of the amplifier circuit. The third capacitor (C3) is required to provide DC separation, otherwise the output (44) of the operational amplifier (4) would be loaded by a high-value DC. The use of a third capacitor (C3), on the other hand, causes an undesired frequency dependence in the lower part of the transmission frequency band in both amplification and output impedance, which can be afforded by the high capacitance selection of the third capacitor (C3). It also results in an undesirable frequency dependence in the gain and output impedance of the finite inductance of the primary winding of the (TI) output transformer.

However, in the circuit arrangement according to the invention, the second capacitor (C2), which is connected in series to the feedback path carrying the current feedback, produces an effect opposite to the effect of the third capacitor (C3) and the output transformer (TI).

The primary winding of the output transformer (TI) is determined by the inductance, the corresponding optimum value of the second, third capacitor (C2, C3), as a function of the required gain and output impedance and accuracy of the amplifier circuit.

In a preferred embodiment of the circuit arrangement according to the invention, the biasing or voltage generating unit (1) consists of a resistor network, a demodulator integrated circuit and a set point circuit, the filter circuit (3) being a low-pass filter, or consisting of an inductance and two capacitors, and the operational amplifier (4) is e.g. Integrated circuit uA 741 or uA 748.

HU 206 005 Β

The switching arrangement of the present invention provides an amplifier circuit having a transmission band of 300 Hz to 3.4 kHz, with an output reflection of min> 20 dB and an output impedance of 600 ohms ± 5%.

The objects and advantages of the circuit arrangement according to the invention are as follows:

- gain is constant over a wide frequency range;

- its output impedance is of the required value and accuracy;

- it can be powered by a single voltage source;

- non-linear distortion of its power loss is small;

- simple construction, economical production,

Claims (1)

Patent Claim Point A switching arrangement for amplifying the power of the received audio frequency signals of transmission equipment having a biasing or voltage generating unit (1) having a control input (11), for supplying a control voltage (11) to the control input (11) of the biasing or voltage generating unit (1). (u _c ) and one half of the power supply voltage (1/2 U.) of a single-cell voltage source, the first output (12) to the fourth input (26) of the demodulator (2), the second output (13) to the third input (25) of the demodulator (2) A modulating voltage (u _m ) is applied to the first and second inputs (21,22) of the (2), the first and second outputs (23, 24) of the demodulator (2) to the second and first inputs (32, 31) of the filter circuit (3). the first output (33) of the filter circuit (3) for one arm of the first capacitor (Cl), the second output (34) for ground, the other arm of the first capacitor (Cl) for operational amplification (4) to the non-inverting input (42) and one end of the first resistor (R1), the other end of the first resistor (R1) to the other end of the second resistor (R2), one end of the second resistor (R2) to the inverting input (4) 41), one end of the third and fourth resistors (R3, R4), the other end of the third resistor (R3) to the output (44) of the operational amplifier (4) and one of the primary windings of the output transformer (TI); junction point of a voltage (43) of the egytelepes voltage source ground point is connected to the egytelepes voltage source is earthed branch (u), another voltage connection point (45), two terminals of the output transformer (TI), the secondary winding of one of the circuit arrangement outputs (u _out) characterized in that one arm of the second capacitor (C2), which feeds back to the other end of the fourth resistor (R4), another armature of the ondenser (C2) for a separator, one arm of the third capacitor (C3) and one end of the fifth resistor (R5), another arm of the third capacitor (C3) for the other terminal of the primary transformer (TI), the other resistor (R5) outputs the same to the ground, the bias hub or a voltage producing unit (1) egytelepes voltage source the supply voltage half (1.2 U) (1) bias voltage (U _E) generating a third end (14) of the first and second resistors (Rl, R2 ) connected to the other end.