JPS62160815A - Amplifier with input disconnection detection circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an amplifier having a function of detecting an input disconnection or an input level of a signal, and particularly relates to an amplifier with an input disconnection detection circuit having a simple circuit configuration.

[Background of the invention]

In order to detect input interruption in conventional circuits that amplify minute input signals, it was necessary to convert the amplified signal amplitude to a DC level using a maximum value detection circuit or the like, and then compare this level with a reference level.

Therefore, there was a problem that the circuit configuration was complicated.

This type of circuit is, for example, "System and Circuit Considerations for Ingrated Industrial Fiber Optic Data Links".
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[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an amplifier with an input disconnection detection circuit that has a simple circuit configuration and has excellent input disconnection detection characteristics.

[Summary of the invention]

The present invention configures a feedback amplifier by connecting a feedback resistor between the input and output of an inverter-type amplifier circuit in which a power supply current flows through the output section, and the power supply current flows in an intermittent manner depending on the signal when a signal is input. This input is made by adding an input disconnection detection circuit that detects an input disconnection based on changes in the DC power supply current, taking advantage of the fact that the DC power supply current decreases when the input is interrupted, and the DC power supply current increases. This is an amplifier with a disconnection detection circuit.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

FIG. 1 shows a first diagram of an amplifier with an input disconnection detection circuit according to the present invention.
It is a circuit diagram showing an example of. In FIG. 1, 1 is an input terminal of an amplifier, 2 is an output terminal, 3 is an input disconnection detection output terminal, 4 is a power supply terminal, 5 is an input disconnection detection circuit, 6 is an inverter type amplifier circuit, 7 is a feedback resistor, 8 is a coupling capacitor. The input disconnection detection port j@5 consists of a resistor 5-1 connected to the power supply terminal 4 and a comparator 5-2, and detects the power supply current I flowing to the power supply terminal 4 by the voltage drop across the resistor 5-1. -2 is used to detect input disconnection and output from output terminal 3. The amplifier circuit 6 has two P terminals between the 1-source terminal 4 and the ground.
It consists of a CMOS inverter circuit in which a type MOS transistor 6-1 and an N-type MOS transistor 6-2 are connected vertically, and has the same configuration as a normal inverter logic circuit. A feedback resistor 7 is provided between the input terminal and the output terminal of the amplifier circuit 6, and the input terminal of the amplifier circuit 6 and the input terminal 1 of the amplifier are connected by a coupling capacitor 8 to form a feedback type amplifier. The resulting signal is amplified and output from output terminal 2.

Note that the same reference numerals or symbols indicate the same or corresponding parts throughout the drawings.

FIG. 2 is an explanatory diagram in which the waveforms of the voltages at the input end and the output end of the amplifier circuit 6 of FIG. 1 and the power supply current I are collectively displayed for cases in which there is an input and cases in which there is no input. The detection operation of the input disconnection detection circuit 5 of FIG. 1 will be explained with reference to FIG. First, when there is no signal input to the input terminal 1, the input terminal and the output terminal of the amplifier circuit 6 are kept at the same potential by the feedback resistor 7.

If the P-type MOS transistor 6-1 and the N-type MOS transistor 6-2 of the CMO 5 of the amplifier circuit 6 are formed with the same dimensions and there is no input disconnection detection circuit 5, this potential is half of the power supply voltage of the power supply terminal 4. The value is . In other words, the power supply current I when there is no input signal is connected to the P-type MOS transistor 6-1 and the N-type MO transistor 6-1 so that the output voltage is half the value of the power supply voltage.
The direct current flowing through the S transistor 6-2 is a DC current m, which has a very large value (FIG. 2). Next, if there is a signal power at the large power terminal 1, the 2 of the amplifier circuit 6
The two P-type MOS transistors 6-1 and the N-type MOS transistors 6-2 perform switching operations, and the power supply current I decreases more than the above-mentioned power supply through-current. If this input signal is large, the power supply current I will be an intermittent current that flows only at changing points (transitions) of the input signal waveform, and the DC component (average value) of the source current 1 (J) will be a very small value. (Figure 2). In this way, as shown in Figure 2, the DC component (average value) of the power supply current I is large when there is no signal input, and becomes small when there is no signal input, so the change in the DC component of the power supply current I is input. Input disconnection can be detected by detection by disconnection detection circuit 5.

FIG. 3 (σl and Ibl are side views of the specific circuit configuration of the input disconnection detection circuit 5 in FIG. 1, respectively. In FIG. 3 (α), the input disconnection detection circuit 5 includes a resistor 5-1 and a transistor 5. -3, the voltage drop that occurs in the resistor 5-1 due to the power supply current I flowing to the power supply terminal 4 is amplified using the transistor 5-3, and the input disconnection detection output is output. The circuit 5 includes, for example, a current detection port 115-4 using the Hall effect and a comparator 5-5), and is a comparator that compares the voltage induced in the current detection circuit 5-4 by the power supply current I with the reference voltage REF. 5-5 to obtain the input disconnection detection output.

Next, FIG. 4 (αl and (bl) are circuit diagrams respectively showing second and third embodiments of an amplifier with a pre-input detection circuit according to the present invention. In contrast to the one-stage C, V05 inverter circuit '#51 thin structure, the amplifier in Fig. .Thus, the amplification factor is increased and the sensitivity of input disconnection detection is increased.The amplifier circuit 6 in Fig. 1 is made of Cu.
Although this is an inverter type amplifier circuit using one O2, the amplifier circuit 6 may be an inverter type amplifier circuit using a plurality of CuO2 or an inverter type amplifier circuit using a biporter transistor.

FIG. 5 (αI, (bl) are circuit diagrams respectively showing the fourth and fifth embodiments of the amplifier with an input disconnection detection circuit according to the present invention.
The configuration is such that the input disconnection detection output is output only to the output terminal 3, but the amplifier shown in FIG.
OS transistor 9-1 and bipolar transistor 9-
2. In this configuration, a power supply cutoff circuit 9 having a 9-3 configuration is added, and the output of the output terminal 3 of the input disconnection detection circuit 5 is input to this. As a result, the power to the amplifier circuit 6 at the subsequent stage is cut off by the input disconnection detection output, thereby preventing an increase in the power supply current and an increase in the power consumption of the amplifier circuit 6 due to the power supply through current when the input is disconnected.

FIG. 6 (αl, (Al) are circuit diagrams respectively showing the sixth and seventh embodiments of the amplifier with an input disconnection detection circuit according to the present invention. It has a configuration in which a power supply cutoff circuit 9 is added to the amplifier circuit 6 shown in FIG. One power supply cutoff circuit 9 for one power supply circuit of one power supply terminal 4-1, or a plurality of power supply terminals 4-1 to 4-
4 Multiple power supply cutoff circuits in other power supply circuits 9-4~
This is a configuration in which 9-7 and others are added. With these, Figure 5 (α).

The same effect as in (h) is obtained, as shown in FIG.
By providing ~9-7 and others, each amplifier circuit 6-1 ~ 6-3
The same effect can be achieved by applying this method to other circuit configurations and cases where the power supply voltage is different.

〔Effect of the invention〕

As explained above, according to the present invention, an amplifier can be configured with a simple circuit and input disconnection can be easily detected using the DC component of the power supply current, so the input disconnection detection is simple in circuit configuration and has excellent input disconnection detection characteristics. An amplifier with a circuit is obtained.

[Brief explanation of drawings]

FIG. 1 shows a first diagram of an amplifier with an input disconnection detection circuit according to the present invention.
2 is a diagram illustrating an example of waveforms at various parts in FIG. α) (Al is the second
．． FIG. 5 (α) is a circuit diagram showing a third embodiment. Ih) is the fourth embodiment according to the present invention. A circuit diagram showing the fifth embodiment, FIG. 6 (αl, (Al is a circuit diagram showing the sixth and seventh embodiments according to the present invention. - Input disconnection detection output terminal 4...Electrical m, terminal 5...Input disconnection detection circuit 6...Inverter type amplifier circuit 7...Feedback resistor 8...Coupling capacitor 9
...Power cut-off circuit patent attorney Masaru Ogawa 11 32 Kasumi 3 Kuchi (b)

Claims (1)

[Claims] 1. An amplifier in which a feedback resistor is connected between the input and output of an inverter-type amplifier circuit in which a power supply through current flows in the output part,
An amplifier with an input disconnection detection circuit, which includes an input disconnection detection circuit that detects an input disconnection based on a change in the power supply through current. 2. The amplifier with an input disconnection detection circuit according to claim 1, wherein the output of the input disconnection detection circuit is connected to a power supply cutoff circuit provided in an amplifier at the next stage of the amplifier.