Features

Low noise: 80 nv P-P (0.1 Hz to 10 Hz), 3 nv/√Hz

Low drifting: 0.2 μV/° C

High-speed speed : 2.8V/μS conversion rate, 8MHz gain bandwidth

Low VOS: 10 μV

Excellent CMRR: 126 DB, VCM is ± 11 v

High -Open Ring gain: 1.8 million

Applicable to OP0755534A socket

Provide in the form of mold

generally explained

OP27 precision operational amplifier puts the low offset, drift and high speed and low speed and low speed and low speed and low speed and low speed and low speed and low speed and low speed and low speed and low speed and low speed and low speed and low speed and low speed and low speed and low speed. Combination of noise. The offset is reduced to 25μV, and the maximum drift is 0.6 μV/° C, making OP27 an ideal choice for the application of precision instruments. Very low noise, EN u003d 3.5 nv/√Hz, at 10 Hz, low 1/F noise rotor frequency is 2.7 Hz, high gain (1.8 million), allowing low -level signals to magnify accurate high gain. The transformation rate of the 8MHz gain bandwidth and 2.8V/μs provides excellent dynamic accuracy in the high -speed data collection system.

By using a bias current to eliminate the circuit, a low input bias current of ± 10NA can be obtained. Within the military temperature range, the circuit usually keeps IB and iOS at ± 20 mAh and 15 mia, respectively.

Have good load driving capabilities. A guaranteed swing ± 10 volt to 600Ω and low output distortion made OP27 the best choice for professional audio applications.

The power suppression ratio and the co -mode inhibitory ratio of more than 120 decibels. These features, plus long -term drift of 0.2 μV/month, enable circuit designers to reach the performance level that previously reached only through discrete design.

The use of the Qina-Zopan fine-tuning network to achieve the low cost and mass production of OP27. After many years of production practice, this reliable and stable biased edge plan is effective.

OP27 has excellent performance in the high precision amplification of low noise and low level signals. Applications include stable integralizers, precision piercing amplifiers, precision voltage threshold detectors, comparators and professional audio circuits, such as magnetic belt heads and microphone front amplifiers.

OP27 is a direct alternative to OP06, OP07 and OP45 amplifier; AD741 amplifier can be directly replaced by removing the zero -adjustment potential meter of AD741.

pin configuration

Figure Figure

Typical performance features

Application information OP27 OP27 The series device can be directly inserted into the OP07 socket to remove external compensation or adjust components. In addition, OP27 can be installed on an unplugged AD741 socket; however, if the traditional AD741 zero -adjustment circuit is used, it should be modified or removed to ensure that OP27 work correctly. The OP27 offset voltage can be adjusted by 0 to 0 (or another required settings) (see Figure 35).

OP27 provides stable operation, with load capacitors as high as 2000 PF and ± 10 V swing; larger capacitors should be decoupled with the 50Ω resistor in the feedback loop. OP27 is a unified gain and stability.

The thermal voltage generated by different metals at the input terminal will reduce the drift performance. When the two input contacts are kept at the same temperature, the best operation can be obtained.

The offset voltage adjustment

The input offset voltage of OP27 is fine -tuned at the wafer level. However, if you need to adjust VOS further, you can use 10 kΩ to fine -tune the potential meter. TCVOS has no downgrade (see Figure 35). Other potential values u200bu200bcan be slightly reduced from 1kΩ to 1MΩ to TCVO (0.1 μV/° C to 0.2 ° C). Values u200bu200bthat are fine -tuned to zero will generate about (VOS/300) μV/° C. For example, if VOS is adjusted to 100 μV, the change of TCVOS to 0.33 μV/° C. The offset voltage adjustment range of 10 kΩ potentiometer is ± 4 mv. If you need a smaller adjustment range, you can reduce the zero -tone sensitivity by using smaller potential meters and fixed resistors. For example, FIG. 36 shows a network with a range of 280 μV.

Noise measurement

To measure the 80 NV P-P noise specifications of OP27 within the range of 0.1 Hz to 10 Hz, the following precautions must be obeyed:

The device must be preheated for at least 5 minutes. As shown in the preheating drifting curve, due to the increase in the temperature of the chip after power, the bias voltage usually changes by 4 μV. Within 10 seconds of measurement intervals, the effects caused by these temperatures can exceed dozens of millivolves.

Out of similar reasons, the device must shield the airflow well. Shielding minimize thermocouple effect.

Sudden exercise near the device may also lead to an increased noise observed.

Measurement test time from 0.1 Hz to 10 Hz noise should not beMore than 10 seconds. As shown in the response curve of the noise test instrument, the 0.1 Hz corner is only defined by one zero. The 10 -second test time is used as an additional zero to eliminate noise contribution of frequency bands below 0.1.

When measuring the noise on a large amount of device, it is recommended to perform the noise voltage density test. 10 Hz noise voltage density measurement value has a good correlation with 0.1 Hz to 10 Hz P-P noise reading, because these two results are determined by the position of white noise and 1/f angle frequency.

Unit's gain buffer application

When the input is driven by fast, large signal pulse ( gt; 1V), the output waveform is shown in the pulse running diagram (see Figure 37) Essence

In the similar fast -feding part of the output, the input protective diode effectively connects the output to the input terminal, and the signal generator will generate a current with only short -circuit protection restrictions. When RF ≥ 500Ω, the output can handle the current requirements (at 10 V IL ≤20 ma); the amplifier remains in the activation mode and a smooth transition occurs.

When RF GT; 2KΩ, the input capacitance (8PF) of the RF and the amplifier forms a pole to generate additional phase shifts and reduce phase margin. Small capacitors (20 PF to 50 PF) with RF eliminate this problem.

Noise Evaluation

OP27 is a very low noise single -piece operation amplifier. The input voltage noise characteristics of OP27 are mainly achieved by operating input levels under high static current. Generally, the input bias current and bias current will be increased by the input bias current to eliminate the circuit. OP27A/E's IB and iOS at 25 ° C are ± 40 na and 35 na, respectively. This is especially important when entering a high -source resistance. In addition, many audio amplifier designers prefer to use direct coupling. The high IB, VOS and TCVOS designed before made it difficult to use directly coupling, if it was not impossible.

The square root of the voltage noise and the bias current is inverse proportional, while the current noise is proportional to the square root of the bias current. When using high -source resistance, the noise advantage of OP27 disappears. Figure 38, Figure 39, and FIG. 40 will compare the OP27's total noise with the noise performance of other devices in different circuits applications.

FIG. 38 shows the relationship between noise and source resistance at 1,000 Hz. The same picture is also suitable for broadband noise. To use this picture, multiply the vertical ratio with a bandwidth.

When RS LT; 1 KΩ, the low -pressure noise of OP27 remains unchanged. When RS LT; 1kΩ, the total noise increases, but mainly from resistance noiseNot current or voltage noise control. Only when the RS exceeds 20kΩ, the current noise begins to dominate. It can be said that current noise is not important for the application of low to medium -sources. The cross between OP27 and OP07 noise appeared in the 15kΩ to 40kΩ area.

FIG. 39 shows 0.1 Hz to 10 Hz P-P noise. The images here are not very good; resistance noise can be ignored, and current noise becomes important because it is inversely proportional to the square root of the frequency. The intersection with OP07 occurs within the range of 3kΩ to 5kΩ, depending on the use of balance or imbalanced source resistance (at 3KΩ, IB and iOS errors can also be three times the VOS specification).

For low -frequency applications, when RS GT; 3 KΩ, OP07 is better than OP27/OP37. The only exception is that the gain error is important.

FIG. 40 shows the noise of 10 Hz. As expected, the results were between the first two numbers.

Table 7 lists the typical source resistance of some signal sources for reference.

Audio application

FIG -C2 uses standard components to form a very accurate RIAA network. The common method of implementing RIAA voice equilibrium is to use frequency related feedback around high -quality gain blocks. Choosing the appropriate RC network can provide three necessary time constants: 3180 μs, 318 μs, and 75μs.

For the initial equilibrium accuracy and stability, it is recommended to use precision metal membrane resistors and film capacitors with polystyrene or polypropylene because they have low voltage coefficients, low losses and low -agent electric absorption. (Here we should avoid using high -K ceramic capacitors, but low -K ceramics, such as NPO types with excellent loss factor and lower dielectric absorption, can consider small value.)

[ 123] OP27 brings a 3.2 NV/√Hz voltage noise and 0.45 PA/√Hz current noise to the circuit. In order to minimize the noise from other sources, R3 is set to 100Ω to generate a voltage noise of 1.3 NV/√Hz. The noise only increases the 3.2nv/√Hz of the amplifier by 0.7DB. For the 1kΩ source, the circuit noise measurement value is lower than the 1MV reference level 63DB in the less width of the 20kHz noise band, and it is not weighted.

The increase of the circuit at 1 kHz (g) can be calculated through the following expression:

The gain is slightly lower than 100 (or 40 decibel). LowerThe gain can be adjusted by increasing R3, but the gain higher than 40DB shows more equilibrium errors due to the 8MHz gain bandwidth of OP27.

This circuit can be very low in the entire range, and is usually less than 0.01%at a level of 7V RMS. At the output level of 3V, it generates a total harmonic distortion of less than 0.03%at a frequency of up to 20kHz.

The capacitor C3 and the resistor R4 form a simple #8722; 6db/times the frequency multiplier dragon filter, and there is an corner at 22Hz. As a choice, the switch selects the parallel container C4, a non -polar electrolytic, bypassing low frequency attenuation. After placing the high -profile effect of the Longlong filter in the front amplifier, the ideal effect can be obtained to identify the low -frequency noise component of the RIAA enlarged and the low -frequency interference generated by the pickup.

The front amplifier used for NAB tape playback is similar to the RIAA sound -primary split large, but usually requires more gain, and a large number of low -frequency enhancements require a large amount of low -frequency. As shown in Figure 42, the circuit in Figure 41 can easily modify it for tape use.

When the tape balance requires a flat high -frequency gain above 3kHz (T2 u003d 50 μs), the amplifier does not need to stabilize the unit gain. OP37 with lost compensation provides a larger bandwidth and conversion rate. For many applications, the ideal time constant shown may require fine -tuning R1 and R2 to optimize the frequency response for non -ideal magnetic head performance and other factors (see the reference data part).

The network value of the configuration generates 50DB gains at 1kHz, and the DC gain is greater than 70dB. Therefore, the output bias of the snail shell is just over 500 millivol to. A 0.47μF output capacitor can block the level without affecting the dynamic range.

The tape head can be coupled to the amplifier input terminal directly, because the bias current at 80 mAh is 400 mAh in the worst case, and 100 μm of the magnet (such as PRB2H7K) is not troublesome.

The bias current of the amplifier can be magnetized to propose a potential tape head problem. OP27 and OP37 have no offset current when power -powered or power off. The speed of controlling power rise and decrease is always conducive to eliminating transient.

In addition, the DC resistance of the magnetic head should be carefully controlled, preferably below 1kΩ. For this configuration, if the magnetic head resistance is not fully controlled, the bias voltage caused by the bias current can be greater than 100PV.

A simple but effective fixed -gain non -transformer microphone front -factor (Figure 43) will be amplified 50dB from the differential signal of low impedance microphone in the future, and the input impedance is 2kΩ. Due to the high working gain of the circuit, OP37 helps to maintain 110 kHzbandwidth. Because OP37 is a loss of compensation device (the minimum stable gain is 5), if the microphone is to be pulled out, a fake resistance RP may be required. Otherwise, 100%feedback from the open input will cause the amplifier to oscillate.

Co -mode input noise suppression depends on the matching of bridge resistance. Types close to the tolerance (0.1%), or the R4 should be trimmed to obtain the best CMRR. All resistors should be metal film types to obtain optimal stability and low noise.

The noise performance of the circuit is limited by the input resistance R1 and R2, not the computing amplifier, because R1 and R2 each generates 4nv/√Hz noise, and the computing amplifier generates 3.2NV/√Hz noise. The sum of the average root value of these main noise sources is about 6nv/√Hz, which is equivalent to 0.9μV at 20KHz noise band width, or nearly 61dB lower than the 1MV input signal. The measurement results confirmed this predictive performance.

For applications that require quite low noise, high -quality microphone transformers coupling the front placed large (Figure 44) contains OP27 containing internal compensation. T1 is a JE115K-E150Ω/15kΩ transformer that provides the best source resistance for the OP27 device. The total gain of this circuit is 40DB, which is the product of the transformer voltage settings and operational amplifier voltage gain.

If necessary, you can adjust the gain to other levels by adjusting R2 or R1. Due to the low offset voltage of the OP27, the output offset of the circuit is very low to the 40 DB gain, which is 1.7 MV or smaller. In this case, typical output blocking capacitors can be eliminated, but higher gains are required to eliminate switch transients.

The capacitor C2 and the resistor R2 form a time constant of 2 μs in this circuit, which is the best transient response recommended by a transformer manufacturer. When using C2, A1 must be unitygain stability. For cases that do not require 2μs time constant, you can delete C2 to use faster OP37.

The 150Ω resistor and R1 and R2 gain resistance connected to the noiseless amplifier to produce a 220 NV noise in the 20 kHz bandwidth, or 73 dB lower than the 1 MV reference level. Any practical amplifier can only approach this noise level, and it will never exceed it. In the absence of OP27 and T1, the additional noise attenuation is close to 3.6 dB (or #8722; 69.5, reference 1 MV).

appearance size

[1], input offset voltage after about 0.5 seconds of power in power for about 0.5 seconds Measurement. A/E level guarantees completely preheating.123]

[2], long -term input offset voltage stability refers to the average trend line of voltage and time after 30 days before running.It does not include the initial hour of running, and the V changes in the first 30 days are usually 2.5 μV.See the typical performance characteristics. [3], see the voltage noise test circuit (Figure 31). [4], guaranteed by the input bias current.

[5], TCV performance is within the scope of the specifications when it is not occupied or R u003d 8kΩ to 20kΩ is zero.TCV 100%test A/E grade, sample test C/G level.

[6] After about 0.5 seconds of power, the input offset voltage measurement is performed by the automatic test device.