Features

Low noise, 80 nv P-P (0.1 Hz to 10 Hz)

3 nv/√Hz@1 kHz

Low drifting, 0.2 volts/degrees Celsius degree

High -speed, 17 volt/second conversion rate 63 MHz gain bandwidth

Low input offset voltage, 10V

excellent co -mode suppression ratio, 126 decibel (11 volt at the time Common voltage)

High-opening gain, 1.8 million

Replace 725, OP-07, SE5534

provided in the form of mold

General description

OP37 provides the same high performance as OP27, but its design has optimized the circuit with a gain of gain greater than 5. This design change increases the conversion rate to 17V/μs, and the gain bandwidth accumulation is increased to 63MHz.

OP37 provides low offset and drift of OP07, as well as higher speed and lower noise. The offset is reduced to 25μV, and the maximum drift is 0.6 μV/° C, making OP37 an ideal choice for the application of precision instruments. Very low noise (en 3.5nv/@10Hz), low 1/f noise angular frequency of 2.7Hz, high gain of 1.8 million, allows high gains to enlarge the high gain of low level signals.

The bias current offsets the circuit to achieve a low input bias current of 10NA and the bias current of 7NA. Within the military temperature range, this usually keeps IB and iOS at 20 mA and 15 mia, respectively.

The output level has good load driving capabilities. Guarantee 10 volts to 600 low output distortion makes OP37 an excellent 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 Qina-Zopi micro-tuning technology to achieve the low cost and mass production of OP37. After many years of production practice, this reliable and stable biased edge plan is effective.

OP37 applies the performance of low noise instruments to microphone, leading and RIAA voice forward placing large, high -speed signal adjustment and broadband instrument in data collection system.

pin connection

Simplified schematic diagram

Typical performance features --P37

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Application information

OP37 series devices can be directly inserted into 725 and OP07 sockets to remove external compensation or adjust components. In addition, OP37 can be installed on the type 741 socket; however, if the traditional 741 zero -adjusting circuit is used, it should be modified or removed to ensure that OP37 work correctly. OP37 offset voltage can use the potential calculation to zero (or other required settings) (see the displacement zero -regulating circuit).

OP37 provides stable operation when the load capacitor is as high as 1000 PF and ± 10 V swing; the larger capacitance should be decoupled with 50 #8486 in the feedback loop. The closed -loop gain must be at least 5. For closed -loop gain between 5 and 10, designers should also consider OP27 and OP37 at the same time. For more than 10 gains, OP37 has obvious advantages than the stable OP27 of Unity.

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

The offset voltage adjustment

The input offset voltage of OP37 is fine -tuned at the wafer level. However, if you need to adjust VOS further, you can use 10 k fine -tuning potential meter. TCVOS is not downgraded (see the bias zero circuit). The value range of other potentials is 1 k to 1 m , TCVO has a slight decrease (0.1 μV/° C to 0.2 μV/° C). Values that 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 will be 0.33 μV/° C. Use 10 k the offset voltage adjustment range of the potential meter is ± 4 mv. If a small adjustment range is required, you can reduce the zero -tone sensitivity by using a smaller potentiometer and a fixed resistor. For example, the adjustment range of the following network is ± 280 μV.

Noise measurement

To measure the noise specifications of 80 NV peaks of OP37 within the range of 0.1 Hz to 10 Hz, the following preventive measures must be observed: [123 123 ]

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 -on, the offset voltage usually changes 4 μV. Within 10 seconds of measurement intervals, these temperature sensing effects 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 feed to increase the observed noise.

Test time from 0.1 Hz to 10 Hz noise should not exceed 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 Hertz noise voltage density measurement value is very correlated with the number of noise reading between the 0.1 and 10hez peaks, because these two results are determined by the position of the white noise and the 1/F corner frequency.

Optimized linearity

By designing the minimum output current required for the application, the best lineivity can be obtained. The peak output current of the operation amplifier is less than ± 10mA, which can obtain high gain and good linearity.

Instrument amplifier

Three lucky amplifier instrument amplifiers provide high gain and broad bandwidth. The input noise of the following circuit is 4.9NV/√Hz. The input -level gain is set to 25, and the second level gain is 40; the total gain is 1,000. The bandwidth of the amplifier with a total gain is a very good precision instrument amplifier. Set to gain 1000, which will generate 800 MHz gain bandwidth. The full power bandwidth of the 20-volt P-P output is 250 kilo. The potential meter R7 provides orthogonal fine -tuning to optimize the communication and co -mode suppression of the instrument amplifier.

Noise Evaluation

OP37 is a very low noise single -piece operation amplifier. OP37's outstanding input voltage noise characteristics are mainly achieved by operating input levels under high static current. The input bias current and bias current are usually added to the input bias current offset the circuit and keep the circuit keep a reasonable value. At 25 ° C, the IB and iOS of OP37A/E are only ± 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.TCVO designed before made it difficult to use direct 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 a high source resistance, the noise advantage of OP37 disappears. Figure 5, 6, and 7 compare the noise performance of total noise observed and other devices observed by OP-37.

Total noise [(voltage noise) 2+ (current noise RS) 2+ (resistance noise_] 1/2

Figure 5 shows the relationship between noise and source resistance at 1000 Hz at 1,000 Hz . The same picture is also applicable to broadband noise. To use this picture, you only need to multiply the vertical ratio on the bandwidth square root.

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When RS LT; 1 K , the low voltage noise of OP37 remains unchanged. When RS LT; 1K total noise increases, but it is mainly controlled by resistance noise rather than current or voltage noise control. Only when the RS exceeds 20KIL can the current noise starts to dominate. It can be said that current noise is not important for the application of low to medium -sources. The cross between OP37 and OP07 and OP08 noise appeared in areas of 15 k to 40 k

Figure 6 shows noise between 0.1 Hz to 10 Hz peaks. Here, the square root of the resistor is inversely proportional to the noise, because the square root of the noise can be ignored. The intersection with OP-07 occurs within the range of 3K to 5K this depends on the use of balance or unbalanced source resistance (at 3K Three times).

Therefore, for low -frequency applications, when RS GT; 3 K OP07 is better than OP27/37. The only exception is that the gain error is important. Figure 3 shows the noise of 10 Hz. As expected, the results were between the first two numbers.

Table one lists a typical source resistance of some signal sources for reference.

Audio application

The following application information is taken from a PMI article on the 12/20/80 electronic design magazine and updated.

FIG. 8 is an example of a voice forward placement of OP27 used for A1; RIAA network. The common method of implementing RIAA voice equilibrium is to use frequency related feedback around high -quality gain blocks. If you choose properly, the RC network can provide three necessary time constants: 3180 μs, 318 μs, and 75μs.

For 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 dielectric absorption. 4 (here should avoid using high-K ceramic capacitors. Although low-K ceramic-such as NPO type, it has excellent loss factors. For small or expensive conditions, you can consider using lower dielectric absorption.)

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, the R3 is set to 100 this will generate 1.3 nv/√Hz. The noise only makes the amplifier's 3.2nv/√HzAdd 0.7db. The noise level measured at 1 kHz at 1 kHz is 1 mvΩ, AΩ.

The gain of the circuit at 1 kHz (G) can be calculated by the following expression:

For the gain of 100 decibels, it shows. By increasing R3, you can adjust the lower gain, but due to the 8MHz gain bandwidth of the OP27, the gain higher than 40DB will show more balance errors.

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 will generate a total harmonic distortion of less than 0.03%at a frequency of up to 20kHz.

Capacitor C3 and resistor R4 form a simple-frequency rondrobic filter-6DB, one corner in 22Hz. As a choice, the switch selects the parallel container C4, a non -polar electrolytic, bypassing low frequency attenuation. After placing the Qualcomm of the Longlong Filter in the front amplifier, it can effectively distinguish the low -frequency noise component of RIAA and the low -frequency interference generated by the pickup.

The front amplifier used for NAB tape playback is similar to the RIAA singer front amplifier, but usually requires more gain, and a large number of low -frequency enhancement requires equilibrium. As shown in Figure 5, the circuit in FIG. 4 can easily modify it to tape use.

Although the tape balancing requires a flat high -frequency gain above 3kHz (T2 50 μs), it does not need to be a stable amplifier for 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 RA and R2 to optimize the frequency response for non -ideal magnetic head performance and other factors

The network value of the configuration generates 50DB gain at 1kHz. And the DC gain is greater than 70dB. Therefore, the output offset in the worst case is only over 500 millivolttil. 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 in the worst case is 85 mAh, the current is 400 mAh, and 100 micro -safety. The head (such as PRB2H7K) is not troublesome.

A potential tape head problem is caused by the dual -current transient transient of the amplifier, which can magnetic the magnetic head. OP27 and OP37 have no offset current when power -powered or power off. However, the speed of controlling power supply is always beneficial to eliminate transients.

In addition, you should carefully control the DC resistance of the magnetic head, preferably below 1K For this configuration, if the magnetic head resistance is not fully controlled, the bias voltage caused by the bias current can be greater than 170PVEssence

A simple but effective fixed -gain non -transformer microphone front placement (Figure 10) In the future, the differential signal of the low impedance microphone is magnified by 50 dB, and the input impedance is 2 k Due to the high working gain of the circuit, OP37 helps maintain a bandwidth of 110 kHz. Because OP37 is a loss -compensation device (minimum stable gain is 5), if the microphone is to be pulled out, a fake resistance RP may be needed. Otherwise, 100%feedback from the open input may cause an amplifier to oscillate.

The input noise suppression of the co -mode input depends on the matching of the bridge resistance ratio. 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 6 nv √Hz, which is equivalent to 0.9μV in 20 kHz noise bandwidth, or nearly 61 dB lower than the LMV 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 device (Figure 11) contains internal compensation. T1 is Je-115K-E150 //15 k transformer, providing the best source resistance for OP27 devices. 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 OP27, the output offset of the circuit will be very low, 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 have a unit gain stability. For cases that do not require 2 μs time constant, C2 can be deleted to allow faster OP37.

Some comments on noise help understand the performance of the circuit. The 150 the resistor and R1 and R2 gain resistors that are connected to the noiseless amplifier will generate 220 NV noise in the 20 kHz bandwidth, or 73 dB of the 1 MV reference level. Any practical amplifier can only approach this noise level, and it will never exceed it. In the case of specified OP27 and T1, additional noise attenuation will be close to 3.6 dB (or -69.5,Reference 1 MV).

The size of the shape

The size unit is inch and (mm).