Features

Low offset voltage: maximum 50 μV

Low offset voltage drifting: Maximum 0.6 μV/° C

Extremely low bias current: maximum 100 PA

very high open Envoy: minimum 2000V/MV

Low power current (each amplifier): maximum 625μA

Work within the range of ± 2 V to ± 20 V

High -common modular suppression: minimum 120 db

[ [ [

123] Response and bridge amplifier

High -stability Thermocouple amplifier

Instrument amplifier

Optical current monitor

High -gain linear amplifier

] Long -term integrator/filter

Sample maintenance amplifier

[[[ 123] Peak detector

Dive amplifier

battery power supply system

Generally Explanation

OP297 is the first industrial standard for industrial standards that packs accuracy to save space. The combination of high -precision, low power consumption and extremely low input bias current makes dual OP297 very useful in various applications.

The accuracy of OP297 includes very low offset (less than 50 μV) and low drift (less than 0.6 μV/° C). Open -loop gain exceeds 2000 volts/millivoltory to ensure the high linearity of each application.

The error caused by the co -mode signal can be eliminated by co -models of more than 120 decibels, thereby minimizing the offset voltage experienced in the battery power supply system. OP297's power supply current is less than 625μA.

OP297 uses an ultra -β input stage with bias current elimination function to maintain at all temperatureHolding the bias current holding the leather tube. This is different from the FET input computing amplifier. Its bias current starts within the range of the Pipanus at 25 ° C, but the temperature will double every 10 ° C to reach the milliam of 85 ° C. The input bias current of OP297 is lower than 100 PA at 25 ° C, and is lower than 450 PA within the military temperature range of each amplifier. This component can work at a power supply voltage of as low as ± 2V.

Combined with accuracy, low power consumption, low bias current, OP297 is an ideal application, including instrument amplifier, a number amplifier, an optical diode front amplifier, and a long -term integralizer. For a single device, see OP97; for the four devices, see OP497.

pin configuration

Application information Very low bias in the wide temperature range The current makes OP297 attractive in the sample maintenance amplifier, peak detector, and the number of amplifiers that must work within the wide temperature range. OP297 does not require a balanced input resistance. Even in the case of imbalance, high -source resistance will only reduce the offset voltage and TCVOS to a minimum.

The input pins of OP297 are protected by the back diode and the current restricted resistance to prevent a large differential voltage. The co -mode voltage of the input terminal is not limited and can be changed throughout the entire range of the power supply voltage.

OP297 is very small for the operation of the power rail, and is specified to run as low as 2 V power. Generally, the scope of the co -mode is expanded to the 1V range of any orbit. When using a 10kΩ load, the output usually fluctuates within the range of 1V.

AC performance

The communication characteristics of OP297 are highly stable in the entire working temperature range. The response of a small signal in unit gain is shown in Figure 26. OP297 is extremely tolerant of the capacitance load at the output end, showing an excellent response under the 1000 PF load (see Figure 27).

Protection and shielding In order to keep OP297 extremely high input impedance, be careful in the layout and manufacturing of the circuit board. The surface of the board must be kept clean and no moisture. It is recommended to use the shelf coating to provide a moisture -proof layer. Even a clean PCB may have a leakage current of 100Pa between adjacent lines, so the protection ring around the input terminal should be used. As shown in Figure 29, the protection tracking works under the voltage close to the input end to minimize the leakage current. In non -changeIn the application, the protection ring should be connected to the co -mode voltage of the inverter input. In reverse applications, both inputs remain on the ground, so the protection tracking should be grounded. The protection line should be set on both sides of the circuit board.

OP7's minimum linear gain is 29mv/29V. This improves the accuracy of OP297 and provides very high accuracy in the high -closed cycle gain application. Figure 30 shows the typical opening gain of OP297 in the military temperature range.

Precision absolute value Putting large device

In an input impedance of 30Ω circuit, the absolute value is 31Ω. OP297's high gain and low TCVOS ensure the precise operation of the micro -input signal. In this circuit, input always appears as a co -mode signal on the operation amplifier. OP297's CMR is more than 120dB, and the error is less than 2PPM.

Figure 32 The maximum output current shown in FIG. 32 is ± 10 mAh. For ± 15 V power, the voltage compliance is ± 10 V. The output impedance of the current transmitter exceeds 3MΩ, and the linearity is better than 16 bits. R1 to R4 should be matching resistors.

In FIG. 33, CH must be polystyrene, Teflon u0026#174; Try to reduce the absorption and leakage of the medium. The drooping rate is determined by the size of CH and the bias current of OP297.

FIG. 34 shows a simple bridge regulatory amplifier using OP297. The transmission function is:

Due to its low input bias current, OP297 is an ideal pair amplifier in non -linear circuit, as shown in Figure 35 and Figure 36 The square and square -rooted circuit shown. Taking the square circuit in Figure 35 as an example, analysis first writes the voltage ring of transistor Q1, transistor Q2, transistor Q3, and crystal tube Q4.

[ 123] On both sides of the equationThe index can get

The operation amplifier A2 forms a current-voltage converter, its output voltage u003d R2 × IOUT.Use (VIN/R1) instead of iin and replace iOut with the previous formula.Function

In these circuits, Iref is a function of negative power supply.In order to maintain accuracy, the negative power should be adjusted well.For applications that need to be very accurate, you can use reference voltage to set iRef.

An important consideration is that a sufficiently large input voltage can force the output to exceed the operating range of the output computing amplifier.Resistance R4 can be changed to Iref or R1; R2 can be changed to keep the output voltage within the available range.

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