JP6325851B2 - Amplifier - Google Patents

Description

  The present invention relates to an amplifying apparatus having a shutdown function.

  The amplifying device 200 is configured as shown in FIG. 4, for example. The transistors Q1 to Q4 and the current source I1 constitute an input circuit for inputting the differential input signals Vin + and Vin−, and the transistors Q5 to Q13 and the current sources I2 to I5 constitute an output circuit. C1 is a feedback capacitor.

  The amplifying apparatus 200 changes from a shutdown state (the currents of the current sources I1 to I5 are zero, the same applies hereinafter) to a power-on state (the currents of the current sources I1 to I5 are predetermined values other than zero, the same applies hereinafter), or When changing from the power-on state to the shutdown state, the period until the potential of each node becomes a predetermined value becomes unstable, and spike noises N1 and N2 as shown in FIG. 5 are generated at the output terminal.

  For this reason, when the amplification device 200 that generates spike noises N1 and N2 is used in a power line communication device, the spike noises N1 and N2 are transmitted to the power line and adversely affect other devices.

  Therefore, when the amplifying apparatus 200 is used for power line communication, as shown in FIG. 6, the switch SW0 is inserted on the output terminal side of the amplifying apparatus 200, and as shown in FIG. When changing from the shutdown state to the power-on state, the switch SW0 is turned on after a predetermined time has elapsed since the amplification device 200 is turned on, and when changing from the power-on state to the shutdown state, the shutdown state By switching off the switch SW0 before shifting to, spike noises N1 and N2 generated at the time of change between the power-on state and the shutdown state are prevented from adversely affecting the power line. In FIG. 6, C2 and C3 are DC cut capacitors, and TR is a transformer.

Japanese Utility Model Publication No. 49-66336

  However, the switch SW0 inserted as shown in FIG. 6 may cause a large current to flow when it is constituted by a transistor, and the on-resistance is reduced in order to prevent deterioration of frequency characteristics and occurrence of distortion. Since it is necessary, the element size is increased, resulting in an increase in cost. Further, when the amplifying device 200 is manufactured by a bipolar process, it is difficult to form the switch SW0 with a bipolar transistor, and an expensive BiCMOS process has to be used, resulting in a further increase in cost.

  An object of the present invention is to provide an amplifying apparatus that prevents spike noises N1 and N2 generated during a change between a power-on state and a shutdown state from adversely affecting a power line and that can realize a low cost. It is.

In order to achieve the above object, the invention according to claim 1 is characterized in that a main amplifier that amplifies an input signal applied to an input terminal and outputs the amplified signal to an output terminal, and amplifies the input signal applied to the input terminal to output the output. e Bei a sub amplifier that outputs to the terminal, the sub-amplifier, from said gain and current output capability than the main amplifier is set small, and previously shutdown state that the main amplifier is changed from a shutdown state to the power-on state In the amplifying apparatus that changes from a power-on state to a shutdown state after the main amplifier changes from a power-on state to a shutdown state, the main amplifier includes a quick charge / discharge circuit, The circuit states that the main amplifier has changed from a shutdown state to a power-on state. , A voltage of the node the feedback capacitor is connected to the rapid discharge in the steady potential, characterized by rapid charging potential of the node when the main amplifier is changed from the power-on state to a shutdown state to the power supply voltage.

According to a second aspect of the present invention, in the amplification device according to the first aspect, the quick charge / discharge circuit has one end of a feedback capacitor of the main amplifier connected to a non-inverting input terminal, and the inverting input terminal is 1 or 2 An operational amplifier connected to a power supply terminal through the above diode, a first switch connected between the inverting input terminal and the power supply terminal of the operational amplifier, and between the feedback capacitor and the power supply terminal And when the main amplifier changes from a shutdown state to a power-on state, the first switch is switched from on to off after the second switch is switched from on to off. The first switch is switched from OFF to ON after the voltage of the node connected to the feedback capacitor is rapidly discharged to a steady state, and the main amplification There when changing from the power-on state to a shutdown state, the second switch is switched from OFF to ON, characterized in that.

  According to the present invention, it is possible to prevent spike noise generated when changing between the power-on state and the shutdown state from adversely affecting the power line, and it is not necessary to connect a large switch to the output terminal. Therefore, cost reduction can be realized.

It is a block diagram of the amplification apparatus of the Example of this invention. FIG. 2 is an operational characteristic diagram of the amplifying device of FIG. 1. It is a circuit diagram of the amplifier of the Example of this invention. It is a circuit diagram of the conventional amplifier. FIG. 5 is an operational characteristic diagram of the amplifying device of FIG. 4. It is explanatory drawing at the time of using the amplifier of FIG. 4 for power line communication. FIG. 7 is an operation characteristic diagram of the amplification device of FIG. 4 in the usage mode of FIG.

  FIG. 1 shows an example in which an amplification device 100 according to an embodiment of the present invention is used for power line communication. A main amplifier 10 amplifies the input differential signals Vin + and Vin− and outputs the amplified signals as an output signal Vout. A sub-amplifier 20 is connected to the main amplifier 10 on the input side and the output side in common, that is, in parallel. The sub-amplifier 20 is set so that the timing of the change from the shutdown state to the power-on state is different from that of the main amplifier 10, and the timing of the change from the power-on state to the shutdown state is also different. .

  That is, as shown in FIG. 2, the sub-amplifier 20 changes from the shutdown state to the power-on state before the main amplifier 10 changes from the shutdown state to the power-on state. Further, after the main amplifier 10 changes from the power-on state to the shutdown state, it changes from the power-on state to the shutdown state. That is, at the timing when the main amplifier 10 changes between the shutdown state and the power-on state, the sub-amplifier 20 is always in the power-on state.

  The gain and current output capability of the sub-amplifier 20 are set to be sufficiently smaller than that of the main amplifier 10, and the output side of the sub-amplifier 20 maintains half the power supply voltage, that is, substantially the midpoint potential.

  Therefore, at the timing when the main amplifier 10 changes between the shutdown state and the power-on state, the sub-amplifier 20 is always in the power-on state, and the output voltage is almost at the midpoint potential. Spike noise is absorbed and reduced by the output side of the sub-amplifier 20.

  Further, when the main amplifier 10 changes between the shutdown state and the power-on state, the circuit is in an unstable state until the voltage of each node becomes a desired voltage, and as described above, the spike noise N1 , N2 are generated. In particular, it takes time to charge and discharge the node to which the feedback capacitor C1 described in FIG. Therefore, in this embodiment, by providing a quick charge / discharge circuit, the charge / discharge time of the node is shortened, the unstable period is shortened, and this also increases the effect of reducing spike noise.

  FIG. 3 shows a specific circuit of the amplifying apparatus 100 of this embodiment. In the main amplifier 10, reference numeral 11 denotes an input circuit that inputs and amplifies input signals Vin + and Vin−, and includes transistors Q1 to Q4 and a current source I1. A rapid charge / discharge circuit 12 includes an operational amplifier OP1, transistors Q14 to Q16, a current source I6, and switches SW1 and SW2. Reference numeral 13 denotes an output circuit for outputting an output signal Vout, which includes transistors Q5 to Q13 and current sources I2 to I5. C1 is a feedback capacitor. The main amplifier 10 differs from the amplifier circuit 200 described in FIG. 4 in that a quick charge / discharge circuit 12 is provided.

  In the sub-amplifier 20, reference numeral 21 denotes an input circuit that inputs and amplifies input signals Vin + and Vin−, and includes transistors Q17 to Q20 and a current source I7. Reference numeral 22 denotes an output circuit that outputs an output signal Vout, which includes transistors Q21 to Q24.

  Now, the amplifying apparatus 100 of the present embodiment is changed from the shutdown state (the currents of the current sources I1 to I7 are zero, the same applies hereinafter) to the power-on state (the currents of the current sources I1 to I7 are a predetermined value other than zero, and the same applies hereinafter). When returning, first, the sub-amplifier 20 is switched from the shutdown state to the power-on state, and first, current starts to flow through the current source I7. Since the amplifying apparatus 100 itself is used with negative feedback (not shown) applied from the terminal of the output voltage Vout to the terminal of the input voltage Vin−, when the current flows through the current source I7, the sub-amplifier 20 becomes the feedback amplifier. The output voltage Vout becomes a desired voltage.

  Thereafter, the main amplifier 10 changes from the shutdown state to the power-on state, the current sources I2 to I6 start to flow current, and the current source I1 starts to flow current with a slight delay. At this time, the main amplifier 10 is in an unstable state until each node approaches a desired potential due to the difference between the current of each of the current sources I1 to I6 and the capacitance of each node. In this unstable state, the collector currents of the transistors Q12 and Q13 do not match, and this current difference becomes spike noise and is mixed into the output voltage Vout.

  However, at this time, since the sub-amplifier 20 is already operating as a feedback amplifier and works to suppress the fluctuation of the output voltage Vout, spike noise generated in the main amplifier 10 is suppressed. Further, in the main amplifier 10, since the current source I1 of the input circuit 11 starts to flow current later than the current sources I2 to I6 of the rapid charge / discharge circuit 12 and the output circuit 13, it is not affected by the input circuit 11 during this period. . In other words, it is not affected by the feedback action.

  When the amplifying apparatus 100 changes from the power-on state to the shutdown state, the sub-amplifier 20 is operating even after the current sources I1 to I6 of the main amplifier 10 become zero, so spike noise generated in the main amplifier 10 Is suppressed by the sub-amplifier 20. Thereafter, the current source I7 becomes zero, and the sub-amplifier 20 enters a shutdown state.

  The rapid charging / discharging circuit 12 is used to quickly settle the voltage at the base of the transistor Q5 (node of the feedback capacitor C1) to a desired value. When the main amplifier 10 is in a shutdown state, the switches SW1 and SW2 are on. Therefore, since the non-inverting input voltage V1 of the operational amplifier OP1 is the power supply voltage Vcc and the inverting input voltage V2 is also Vcc, V1 = V2, and the transistor Q16 is turned off by the operational amplifier OP1. The charge of the feedback capacitor C1 is Vcc.

  Next, when switching to the power-on state, the current source I1 of the sub-amplifier 20 starts flowing current, and at the same time, the switch SW2 of the main amplifier 10 is turned off. Then, a current starts to flow through the current sources I2 to I6, a current starts to flow into the current source I1 with a delay, and then the switch SW1 of the main amplifier 10 is turned off. At this time, the voltage V1 = Vcc and the voltage V2 = Vcc−2Vbe, which are compared by the operational amplifier OP1, and V2 <V1, so that the transistor Q16 is turned on, the charge of the feedback capacitor C1 is discharged, and the voltage V1 is descend. Thus, when V1 = V2, the transistor Q16 is turned off and the switch SW2 is turned on.

  Thus, when changing from the shutdown state to the power-on state, the voltage V1 at the base of the transistor Q5 is quickly discharged from the voltage Vcc and becomes a steady state, and the period of the unstable state of the main amplifier 10 is shortened. Noise can be reduced.

  When the power-on state is changed to the shutdown state, the switch SW2 is turned on, the base voltage V1 of the transistor Q5 is quickly charged to the voltage Vcc, and the period of the unstable state of the main amplifier 10 is shortened. , Spike noise can be reduced.

  In FIG. 3, a series circuit of two diodes is connected in parallel to the switch SW1, but the number of diodes may be one or two or more.

DESCRIPTION OF SYMBOLS 100: Amplifier 10: Main amplifier, 11: Input circuit, 12: Rapid charge / discharge circuit, 13: Output circuit 20: Sub amplifier, 21: Input circuit, 22: Output circuit

Claims (2)

A main amplifier for amplifying an input signal applied to the input terminal to the output terminal, said amplifies the input signal applied to the input terminal e Bei a sub amplifier output to said output terminal, said sub-amplifier, The gain and current output capability are set smaller than the main amplifier, and the main amplifier changes from the shutdown state to the power on state before the main amplifier changes from the shutdown state to the power on state. In an amplifying apparatus that changes from a power-on state to a shutdown state after changing to a shutdown state ,
The main amplifier includes a rapid charge / discharge circuit, and the rapid charge / discharge circuit rapidly discharges a voltage of a node to which a feedback capacitor is connected to a steady potential when the main amplifier changes from a shutdown state to a power-on state. An amplifying apparatus characterized in that when the main amplifier changes from a power-on state to a shutdown state, the potential of the node is rapidly charged to a power supply voltage . The amplifying apparatus according to claim 1 , wherein the rapid charge / discharge circuit includes:
An operational amplifier in which one end of the feedback capacitor of the main amplifier is connected to a non-inverting input terminal, and the inverting input terminal is connected to a power supply terminal via one or more diodes;
A first switch connected between the inverting input terminal of the operational amplifier and the power supply terminal;
A second switch connected between the feedback capacitor and the power supply terminal;
With
When the main amplifier changes from a shutdown state to a power-on state, the first switch is switched from on to off after the second switch is switched from on to off, and a node to which the feedback capacitor is connected The first switch switches from off to on after rapidly discharging the voltage to a steady state;
When the main amplifier changes from a power-on state to a shutdown state, the second switch switches from off to on;
An amplifying device characterized by that.

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