JPH03211956A - Signal amplifying output circuit - Google Patents

Abstract

PURPOSE:To obtain a double amplitude and to normally send out a signal without crashing the waveform of a touch tone, for example, by synthesizing two output waveforms by using two operational amplifiers. CONSTITUTION:A separated transformer 31 is provided to be connected to a line 33 and operational amplifiers 30 and 32 are provided to be connected at the both ends of the separated transformer 31 so as to input the output of an inverse phase through a matching resistor 37. Then, the waveform, which waveform is inverted to the output of the operational amplifier 30, is outputted. Thus, the output synthesizing the two output waveforms of the two operational amplifiers 30 and 32 is sent out to the line 33 and the double amplifying operation is sufficiently executed. Then, the output signal wave form such as a DTMF (Dual Tone Multiple Frequency), etc., for example, is not crashed and touble caused by the exactness of amplification can be prevented.

Description

[Detailed Description of the Invention] [Summary] Regarding a signal amplification output circuit that amplifies and outputs a transmission signal, the purpose of the present invention is to provide a signal amplification output circuit that can obtain sufficient amplitude, and which is connected to a line by a separation transformer. , in a signal amplification output circuit that transmits and outputs a transmission signal, two of the line separation transformers
By connecting the output of an operational amplifier with an opposite phase to both ends of the next side through a matching resistor, the output amplitude of the operational amplifier can be doubled.
It was configured to obtain double the signal amplitude.

[Industrial Application Field] The present invention relates to a signal amplification output circuit that amplifies and outputs a transmission signal.

For example, consider a modem that can be powered by a battery and operates on a single +5V voltage. The modem must function normally no matter what the power source is, but +5
When operating with a single v, there is a phenomenon in which touch tones are not sent out properly.

The touch tone transmission procedure begins with the DTMF from the MPU.
(Dual Tone Multiple Fre
)) A command to send a touch tone arrives at the transceiver. Therefore, the DTMF) transceiver sends out the specified DTMF. The DTMF is amplified by an operational amplifier and sent to the line.

The reason why touchtones are not being sent properly is that the DTMF when sent to the line is not considered to be the specified frequency, so it does not function normally (does not dial the other party, confirm the dialed number, etc.) .

Therefore, it is necessary to ensure that the DTMF frequency satisfies the regulations in order to operate the modem normally. For this purpose, it is necessary to make the operational range of amplification of the operational amplifier sufficiently large.

[Prior Art] An example of a conventional signal amplification output circuit used in a modem for transmitting a touch tone is shown in FIG.

In FIG. 4, data from the data terminal device 1 is DT
The signal passes through the E interface 2 and the MPU 3, is modulated by the modem section 4, is amplified by the operational amplifier 5, and then input to the analog switch 6.

Further, according to instructions from the MPU 3, the DTMF sending circuit 7 sends out the designated DTMF, and inputs it to the analog switch 6 via the analog switch 8.

The analog switch 6 switches data or DTMF according to instructions from the MPU 3, and its output is sent to an operational amplifier 9.
is amplified. The output of operational amplifier 9 is line transformer 1
0 to a station not shown on the line 11.

Data from the station is input to the operational amplifier 12 via the line transformer 10, amplified by the operational amplifier 12, passed through the analog switch 8, amplified again by the operational amplifier 13, demodulated by the modem section 4, and then sent to the MPU 3. ,D
The data is input to the data terminal device 1 via the TE interface 2.

Here, the output waveform of the operational amplifier 9, which is a signal amplification output circuit, is shown in A of FIG. 5, and the output waveform of the ground side of the line transformer 10 is shown in B of FIG. 5, and the waveforms of A and B are shown in FIG. The combined result is sent out from the line 11. Now, if the amplitude of the waveform of A is fl, the amplitude of the waveform sent to the line 11 is also fl.

[Problems to be Solved by the Invention] However, in such a conventional signal amplification output circuit, when operating with a single +5V power supply, the output voltage is 3.5V and the amplitude is ±1°. 7V, the amplification effect is not sufficiently performed, and the operating range of the amplification is narrow, so there is a problem that sufficient amplitude cannot be obtained. For this reason, for example, the DTMF waveform becomes a flattened trapezoid, which does not satisfy the specified frequency, resulting in malfunctions such as not dialing the other party or misidentification of the dialed number.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a signal amplification output circuit that can obtain a sufficient amplitude.

[Means to solve the problem] FIG. 1 is a diagram explaining the principle of the present invention.

31 is a separation transformer connected to the line 33, and 30.degree. 32 is an operational amplifier connected to both ends of the separation transformer 31 through a matching resistor 37 so that outputs of opposite phases are inputted thereto.

[Function] In the present invention, in addition to the operational amplifier 30, another operational amplifier 32 is provided to output a waveform whose phase is reversed from the output of the operational amplifier 30. A combination of the two output waveforms is sent to the line 33.

Therefore, even when the output of the operational amplifier 30 is output to the line 33 side, a sufficient double amplification effect is achieved. Therefore, the output signal waveform of DTMP etc. will not be distorted (and the DTMF frequency will meet the regulations, so you will not be able to dial the other party or misread the dialed number, and it will work normally.) It is possible to improve the conventional disadvantages caused by the accuracy of amplification, such as when DTMF is sent out.

As a result, the modem can operate normally and improve reliability.

[Example] Embodiments of the present invention will be described below based on the drawings.

FIGS. 2 and 3 are diagrams showing one embodiment of the present invention.

In FIG. 2, 21 is a data terminal device, and the data terminal device 21 connects the MP via a DTE interface 22.
Connected to U23. 24 is a modem unit that demodulates data; 25 is a DTMF that sends out DTMF;
The modem section 24 and the DTMF sending circuit 25 are controlled by the MPU 23. The data modulated by the modem section 24 is amplified by an operational amplifier 26 and then input to an analog switch 27. Further, the DTMF sent out from the DTMF sending circuit 25 is transmitted to the analog switch 28.
The signal is input to the analog switch 27 through the .

Analog switch 27 performs data or DTMF switching.

Reference numeral 30 denotes an operational amplifier, which is an operational amplifier. The operational amplifier 30 amplifies the output of the analog switch 27, and its output side is connected to one end of a line transformer 31, which is a separation transformer. Reference numeral 32 denotes an operational amplifier which is another operational amplifier. The output of the operational amplifier 30 is input to the operational amplifier 32, and the output side is connected to the other end side of the line transformer 31. The operational amplifier 32 outputs a waveform whose phase is reversed from that of the output waveform of the operational amplifier 30.

The line transformer 31 is connected to a station (not shown) via a line 33, and an operational amplifier 34 for amplifying data from the station is also connected to the line transformer 31. The output of the operational amplifier 34 passes through the analog switch 28 to the operational amplifier 3.
5, and after being amplified by the operational amplifier 35, the signal is input to the modem section 24. The modem section 24 demodulates the data,
The demodulated data is input to the data terminal device 21 via the MPU 23 and the DTE interface 22.

Next, the operation will be explained.

The MPU 23 instructs the DTMF sending circuit 25 to send out the DTMF, and the DTMF sending circuit 25 sends out the designated DTMF. DTMF is selected by analog switches 28 and 27 controlled by MPU 23 and operational amplifier 30
and is amplified by the operational amplifier 30. The output of this operational amplifier 30 is shown at C in FIG. The output waveform of the operational amplifier 30 is input to the operational amplifier 32, and the operational amplifier 32 outputs a waveform whose phase is reversed from waveform C (see Fig. 3).
reference).

A composite of the output waveform C of the operational amplifier 30 and the output waveform of the operational amplifier 32 is sent to the line 33 via the line transformer 31. Now, the amplitude of the waveform of C is f2, D
If the amplitude of the waveform C9D is f3, the waveform sent to the line 33 is the sum of the changes of the two waveforms C9D, so its amplitude is f2 + f3. Here, fl
Since =f2 =f3, the amplitude of the composite waveform sent to the line 33 is doubled.

In this way, even when operating with a single power supply, since the two operational amplifiers 30 and 32 are used for amplification, the amplification effect is sufficient and the amplification ability is not saturated. Therefore, for example, the DTMF waveform is not distorted and satisfies the specified frequency. As a result, problems such as not dialing the other party or misidentification of dialed numbers do not occur, and touch tones are transmitted normally.

[Effects of the Invention] As described above, according to the present invention, two operational amplifiers are used to synthesize two output waveforms, so twice the amplitude can be obtained. Therefore, for example, the waveform of the touch tone is not distorted and the frequency of the touch tone satisfies the regulations, so that the touch tone is transmitted normally.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a diagram showing an embodiment of the present invention, Fig. 3 is an output waveform diagram of an operational amplifier, Fig. 4 is a diagram showing a conventional example, and Fig. 5 is a diagram showing a conventional example. FIG. 2 is an output waveform diagram of an operational amplifier. In the figure, 21...Data terminal device, 22...DTE interface, 23...MPU. 24... Modem section, 25... DTMF sending circuit, 26... Operational amplifier, 27.28... Analog switch, 30... Operational amplifier (operational amplifier) 31... Line transformer, 32 ...Operational amplifier (operational amplifier) 33...Line, 34.35...Operational amplifier.

Claims (1)

[Claims] In a signal amplification output circuit that is connected to a line (33) by a separation transformer (31) and transmits and outputs a transmission signal, an opposite phase calculation is applied to both ends of the secondary side of the separation transformer (31) of the line (33). The outputs of the amplifiers (30) and (32) are connected to matching resistors (
By connecting through the operational amplifier (37)
) A signal amplification output circuit characterized in that it obtains a signal amplitude twice as large as the output amplitude of the circuit.