JPS60145709A - Drift compensating amplifying device - Google Patents

Abstract

PURPOSE:To reduce always a drift quantity by switching the output of an amplifier to that of a holding circuit to connect the output of the holding circuit to an output terminal during drift compensation. CONSTITUTION:Before switches 25 and 26 are changed over, only an amplifier 21 performs one-stage operation. When an output is outputted from a switch 27 to change over switches 25 and 26, the input of the amplifier 21 is connected to a reference bias 24, and the output is connected to the input of a drift compensating circuit 22, and drift compensation is performed. At this time, the output of a holding circuit 23 is connected to an output terminal 29 of this amplifying device, and the outpt voltage value of the amplifier 21 just before switching of the switch 26 is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an amplification device for correcting the drift of an amplifier that amplifies an electrical signal.

Conventional configurations and their problems In recent years, with dramatic advances in the performance of control devices, measuring devices, etc., demands for higher levels of performance of the amplifiers used in these devices have become increasingly strict. be. Above all,
Amplifier output level temperature.

Fluctuations due to humidity and other ambient conditions, that is, drift, are also considered to be the most important factor in the demand for higher levels.

Therefore, integrated circuits (hereinafter referred to as ICs) that are stable against environmental conditions such as temperature and humidity or changes over time have been developed and put into practical use as amplifiers, but they are expensive and do not meet the actual requirements. In addition, even the most excellent IC cannot cope with changes in the constants of peripheral circuits, and cannot satisfy the level requirements beyond a certain level.

Furthermore, as a supplement to this, there is a device that captures fluctuations in the output of the amplifier and feeds back an amount that restores the fluctuations to the input of the amplifier.

This device sets the input of the amplifier to a constant value, measures the variation in the output with respect to the predetermined value, and biases the value at the input of the amplifier so that the variation is canceled out. be. Hereinafter, this device will be referred to as a drift correction device.

Next, a conventional example will be explained using figures.

FIG. 1 shows a conventional drift correction device.

It is a 1-digit amplifier, 2 is its input resistance, and 3-digit offset adjustment resistor.If the amplifier is an IC, etc., it can be used to cope with ambient constants, etc., and to perform high-precision offset adjustment. It is being used as an example. Therefore, although drift correction can also be performed by controlling this offset adjustment resistor, this method will not be used in the description of this conventional example.

4 is a drift correction circuit, which inputs the output of the amplifier 1 into the drift arm 1F circuit 4 and adds an appropriate correction amount to the input of the amplifier 1. Shown in Figure 2. In Figure 2, 6
The polarity and operating voltage of each of the seven comparators are determined by the reference power supplies 8 and 9. In this conventional example, a
Depending on the voltage at the point, comparator 6 operates on the negative side and comparator 7 on the positive side. 1o is an oscillator, the output of which and the output of comparator 6 enter gate 11, and the output of comparator 7 also enters gate 1-12.

Both gates 11 and 12 are ant gates, gate 11 is connected to the down count input of the reversible counter 13, and gate 12 is connected to the up count input of the reversible counter 13. Corresponding to each pit from the reversible counter 13,
It is connected to the D/A converter 14 and converted into a voltage by an operational amplifier 16 connected to the output of the D/A converter 14.

Next, the operations in FIGS. 1 and 2 will be explained. When the voltage at point a shifts to the negative side, if this voltage further exceeds the voltage of the reference power supply 8, an output is generated from the comparator 6.

This stop gate 11 is opened and a pulse from the oscillator 1° is applied to the down-count input of the counter 13. As a result, the counter 13 counts down, and the voltage output by the DA converter 14 and the operational amplifier 16 (point b) also shifts to negative (to IIll). Since this voltage is applied to the amplifier 1 through the input resistor 6 in FIG. 1 is corrected in the positive direction. When the output of the amplifier is lower than the voltage of the reference power supply 8 in FIG. 2, the gate 11 is closed and no pulse is applied to the counter 13, so the potential at point b does not change any further,
This value is held and the voltage continues to be supplied to the amplifier 1 in FIG. The above operations complete the drift correction. Further, since the same is true when the voltage at a-imaginary shifts to the positive side, the explanation will be omitted.

However, with the above configuration, while the amplifier is operating, it is not known whether the change in output is due to drift or the input signal, so it is difficult to prevent drift that occurs during operation, such as when the amplifier is used in continuous operation. I can't. Therefore, when used continuously, it has serious drawbacks, such as the need to interrupt operation and perform drift compensation [F], and the need to use an amplifier with a single high pitch that has little drift.

OBJECTS OF THE INVENTION The present invention solves these conventional problems, and aims to provide a good drift correction amplifier device with a small amount of drift at all times.

Structure of the Invention The present invention includes one or more amplifiers, a drift correction circuit that outputs a drift correction amount by detecting the output of the amplifier and restoring the drift of the amplifier, and holding the output of the amplifier described in item IJ. a halt circuit, a switch device that connects the input of the one or more amplifiers to the reference power supply, the output to the 1-lift correction circuit, and switches the connection to the output terminal from the output of the amplifier to the hold circuit; and this switch. A drift correction amplifier device characterized by having a switching device for switching and driving the device, and which can always keep the amount of drift small by connecting a hold circuit instead of the output of the amplifier during drift correction. It is. Also,
It is not necessary to use an expensive IC with little drift.

DESCRIPTION OF EMBODIMENTS FIG. 3 is a block diagram of an actual winding example of the present invention. Third
In the figure, 21 is an amplifier, and 22 is a drift sleeve +F circuit, the internal configuration of which is the same as that of the conventional example. father,
23 is a hold circuit which inputs the output voltage of the amplifier 21 and holds that voltage.0, 24 is a reference bias during drift correction, and in the case of normal drift correction, ○
It's a bolt. 25 and 26 are switches respectively, 25 connects either the amplifier input terminal 28 or the reference bias 24 to the input of the amplifier 21, and the switch 26 connects the amplifier 21
The output of the drift correction circuit 22. It is connected to either the hold circuit 23 or the amplifier output terminal 29,
Switches 26 and 26 are both J'1. are also switched at the same time.

Note that the switch states in the figure are states during normal operation of the amplifier 21. Reference numeral 27 denotes a switch which controls switching of the switches 26 and 26 at the same time.

Next, the operation of this example will be explained. Assume that the switches 26 and 26 are each in the following state as an initial state. That is, the input of the amplifier 21 is connected to the amplifier input terminal 28, and the output is connected to the input of the hold circuit 23 and the amplifier output terminal 29, respectively. Note that the output of the drift correction circuit 22 is always connected to the input of the amplifier 21 via a resistor. In the above state, only the amplifier 21 is performing general operation, and no drift correction operation, output voltage halt, etc. are performed. Next, when the output is output from the switch 27 and the switches 26 and 26 are turned on, the amplifier 2
The input of 1 is connected to the reference bias 24, and the output is connected to the input of the drift correction circuit 22. The connection to the amplifier output terminal 29 is from the output of the amplifier 21 to the hold circuit 2.
Switched to connect to output 3.

The operation of each part in this switch state will be explained next.

Since a reference bias is connected to the input of the amplifier 21, an output corresponding to the reference bias can be obtained from the output of the amplifier 21. The manual part of the drift correction circuit 22 compares it with a predetermined reference value, and if the output voltage of the amplifier 21 is deviated, outputs a correction value and adds it to the input of the amplifier 21. With this input, the output of the amplifier 21 approaches the predetermined reference value of the input part of the drift correction circuit 220, but if there is a deviation, the correction amount is increased according to the deviation meter. Therefore, the output of the amplifier 21 and the drift sleeve Ito circuit 2
This control loop operates until the difference from the predetermined reference value of the input section 2 becomes almost 0, and the drift correction circuit 22
Drift correction is complete when the output no longer changes. In addition, in the explanation of the first ffF, the correction amount is too large,
If the output of the amplifier 21 is inverted in magnitude with respect to the predetermined reference value of the input section of the drift correction circuit 22, or exceeds the predetermined reference value on the opposite polarity side of the input section of the drift correction circuit 22, the amount of correction is reduced. , the first one performs the opposite operation, and the control loop shifts to a stable direction.

At this time, the hold circuit 23 is connected to the amplifier output terminal 29.
The output of the amplifier 21 is connected to the connection M, and the output voltage value of the amplifier 21 immediately before the switch 26 is switched is outputted by the switch 27. The internal configuration of this hold circuit 23 may be composed of only the simplest capacitor, but it is common to use a FIT or an operational amplifier, etc. Omitted.

Note that the predetermined reference value and the reverse polarity side predetermined reference value are set by the reference power supplies 8 and 9.

Now, the switches 25 and 26 are switched by the drive output of the switch 27, and if the switching speed is reduced, each hold time of the hold circuit 23 is shortened, so that the delay in response to a voltage change at the amplifier input terminal 28 is also shortened. It ceases to be a head. In other words, the delay Tp in this system is TD = TA + TSH, where TA is the delay of the amplifier and TSH is the hold time of the halt circuit, and TSH becomes smaller as the switching speed increases, so Tp becomes smaller. Become.

As described above, according to this example, the drift correction operation is performed in a time-division manner by the output of the switch 2, and at the same time, the output is held by the hold circuit 23 during that time, so that the drift is corrected one by one. It is possible to obtain an amplifier 91 that is corrected and can be used at all times as in the normal state. Also, in this case, it is not necessary to use an expensive IC with little drift as the amplifier IC.

Effects of the Invention The present invention comprises one or more amplifiers, a drift compensator 11-' which detects the output of the amplifier and restores the drift of the amplifier;
) a drift correction circuit that outputs i-j, a hold circuit that holds the output of the amplifier, the input of the one or more amplifiers is connected to the reference power supply, the output is connected to the drift correction circuit, and the output terminal is connected to the output terminal. A drift correction amplifier device comprising a switch device for switching the connection from the output of the amplifier to a hold circuit, and a switch device for switching and driving the switch device, and a switch device for switching the connection between the drift correction circuit and the hold circuit. This is an excellent device that can constantly correct the amount of drift by switching by the switching operation of the switch device driven by the drive, and can provide a drift correction amplifier that can be used at all times as in the normal state. It also has the advantage that it is not necessary to use an expensive amplifier with little drift.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional drift correction amplifier, FIG. 2 is a block diagram of a drift correction circuit in a conventional example, and FIG. 3 is a block diagram of a drift correction amplifier according to an embodiment of the present invention. It is a diagram. 21...Amplifier, 22...Drift compensation iE circuit, 23...Hold circuit, 25.26...Switch, 27...Switcher. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Ward 2nd page 3 Figure 7

Claims (1)

[Claims] one or more amplifiers, a drift correction circuit that detects the output of the amplifier and outputs a drift correction l: that restores the drift of the amplifier, a hold circuit that holds the output of the amplifier, and one or more of the amplifiers. a switch device that connects the input of the amplifier to the reference power supply and the output to the drift correction circuit, connects the output terminal to the output terminal, and switches the output of the amplifier to the hold circuit; and a switch that switches and drives the switch device. A drift correction amplifier comprising: