Features

Low -voltage noise: 1 kHz is 1.1 nv/√Hz

Input voltage noise: 80 nvpp (0.1 Hz to 10 Hz) [ 123]

THD+N: - 136DB (g u003d 1, f u003d 1 kHz)

offset voltage: 125μV (maximum)

#8226; offset voltage drift: 0.35μV/° C (typical value)

Low power current: 3.6 mA/CH (typical value)

unified unified Stability of gain

gain bandwidth product:

80 MMH (100 Mix He)

45 MMH (G u003d 1)

#8226 ; Conversion rate: 27 v/μs

16 -bit settings: 700 ns

Wide power supply range: ± 2.25 V to ± 18 V, 4.5 V to 36 V

Rail transfers

output current: 30 ma

PLL ring circuit Filter

Low noise, low power signal processing

16 -bit ADC driver

DAC output amplifier [123 123 ]

active filter

Low noise instrument amplifier

Ultrasonic amplifier

Professional audio audio Pre -Player

Low noise frequency synthesizer

Infrared detector amplifier

Water hearing amplifier

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123] Rapidifier

Medical

Support extreme temperature applications

Controlled baseline

#8226; A assembly/test site

A manufacturing site

Extreme temperature range (-55 ° C/210 ° C)

extend the product life cycle

extend the product change notice

Product traceability

Texas Instruments High -temperature products adopt a highly optimized silicon (mold) solution, which has design The process improvement function can maximize performance at the maximum extension of the temperature.

Explanation

OPA211 series precision operational amplifier achieves very low 1.1NV/√Hz noise density, and the power supply current is only 3.6mA. The series also provides rails to swing, maximizing the dynamic range.

The extremely low voltage and low -current noise, high -speed and wide output swing of the OPA211 series make these devices the best choice for the PLL application Central circuit filter amplifier.

In the precision data acquisition application, the OPA211 series operational amplifier provides a stable time of 700 nan seconds, reaching 16 -bit accuracy of 10 volt output swing. This communication performance, plus only 125 μV's offset and temperature drift of 0.35 μV/° C, making OPA211 a driver of high -precision 16 -bit modulus converter (ADC) or buffer high -resolution digital modulus converter (DAC ) The ideal choice of output.

The OPA211 series is suitable for a wide dual -power supply range of ± 2.25 V to ± 18 V, or a single power operation of 4.5 V to 36 V.

The specified range of the operation amplifier in this series is TA u003d –55 ° C to 210 ° C.

(1), the custom temperature range

Typical feature [ 123]

Unless otherwise explained, TA u003d 25 ° C, VS u003d ± 18 V, RL u003d 10 K .

] Application information OPA211 is an operational amplifier with a stable unit gain and very low accuracy. The application of noise or high impedance power supply requires the degraded capacitor pins near the device. In most cases, 0.1-μF capacitors are enough. Figure 42 shows the simplified schematic diagram of OPA211. The chip uses the SIGE bipolar process and contains 180 transistors. Working voltage OPA211 series operational amplifier can work within the range of ± 2.25-V to ± 18-V power supply, while maintaining excellent performance. OPA211 series of power supply between the power supplyThe voltage is only 4.5 volts, and the voltage between the power supply can reach up to 36 volts. However, some applications do not require the same positive and negative output voltage. For the OPA211 series, the power supply voltage does not need to be equal. For example, the positive power supply can be set to 25 V, and the negative power supply is set to -5 V, and vice versa. The co -mode voltage must be kept within the specified range. In addition, key parameters are guaranteed within the specified temperature range, and TA u003d --55 ° C to 210 ° C. The typical feature shows the parameters that significantly changes with the working voltage or temperature.

Input protection

As shown in Figure 211-211, there is excessive voltage differential protection between the input and input end of OPA-43. In most circuit applications, there are no consequences of input protection circuits. However, in a low -gain or G u003d 1 circuit, because the output of the amplifier cannot respond enough to the input slope, the fast slope input signal can make these diode offset forward. Typical features Figure 30 illustrate this impact. If the input signal is fast enough to generate this positive bias condition, the input signal current must be limited to 10mA or below. If the input signal current is not restricted by in good condition, you can use the input series resistor to limit the signal input. This input series resistance reduces the low noise performance of OPA211, and discusses worksheets in the noise performance part of this data. FIG. 43 shows an example of a current -limiting feedback resistor.

Noise performance (1)

FIG. 44 shows the op amp that the unit gain configuration (no feedback resistance network, so there is no additional noise contribution) General circuit noise of source impedance changes. Two different operational amplifiers display and general circuit noise calculation. OPA211 has a very low voltage noise, making it an ideal choice for low source impedance (less than 2K ). A similar precision computing amplifier, OPA227, has high voltage noise, but lower current noise. It provides excellent noise performance under medium source impedance (10K to 100K ). At 100K above, FET input computing amplifier, such as OPA132 (very low current noise) can provide better performance. The formula in FIG. 44 is used to calculate the entire circuit noise. Pay attention to EN u003d voltage noise, IN u003d current noise, RS u003d source impedance, K u003d Bolzman constant u003d 1.38 × 10–23 j/k, T is temperature (unit: K).

Basic noise calculation

The design of the low noise computing amplifier circuit needs to carefully consider various possible noise factors: noise from the signal source, in the operation amplifier The noise generated and noise from the feedback network resistor. The total noise of the circuit isThere is a square root and combination of noise component.

The resistance part of the source impedance generates the heat noise of proportion to the square root of the resistance. This function is shown in Figure 44. The source impedance is usually fixed; therefore, the choice of op amp and feedback resistance to minimize the contribution of their total noise.

FIG. 44 depicts the total noise of different source impedances of the op amp in the unit gain configuration (no feedback resistance network, so there is no additional noise contribution). The operation amplifier itself generates voltage noise components and current noise components. The voltage noise is usually modified as the time to change the component of the bias voltage. The current noise is modeled to the time variable in the input bias current and reacts with the source resistance to generate noise. Therefore, the minimum noise computing amplifier given by a given application depends on the source impedance. For low -source impedance, current noise can be ignored, and voltage noise usually dominates. For high -source impedance, current noise may dominate.

FIG. 45 illustrates the configuration of the inverter and non -inverter operation amplifier circuit. In the configuration of the gains, the feedback network resistance will also produce noise. The current noise of the amplifier and the feedback resistor reaction to generate additional noise components. The feedback resistance value can usually be selected so that these noise sources can be ignored. The total noise equation of the two structures is given.

Total harmonic distortion measurement

OPA211 series operational amplifier has excellent distortion characteristics. THD+noise is lower than 0.0001%(g u003d 1, VO u003d 3VRMS), 20 Hz to 20 kHz within the entire audio range, and 600Ω.

The distortion generated by the OPA211 series operations amplifier is lower than the measurement limit of many commercial distortion analyzers. However, the special test circuit shown in FIG. 46 can be used to expand measurement capabilities.

The operational amplifier distortion can be considered as an internal error source, and you can refer to the input. FIG. 46 shows a circuit that makes the incompeters of the computing amplifier 101 times larger than the distortion that is usually produced by the operation amplifier. Adding R3 to other standards of non -mute amplifier configuration will change the feedback coefficient or noise gain of the circuit. The closed -loop gain is unchanged, but the feedback that can be used for error correction is reduced by 101 times, which increases the resolution by 101 times. Note that the input signals and loads on the computing amplifier are the same as the traditional feedback without R3. The value of R3 should be kept smaller to minimize its impact on distortion measurement.

The effectiveness of this technology can be verified by repeated measurement under high gain and/or high frequency, where the distortion is within the measurement capacity range of the test equipment. The measurement of this data table uses the dual distortion/noise analyzer of the audio precision system, which greatly simplifies repeated measurement. However, the measurement technology can be executed by manual distortion measuring instruments.

Turn off

Close (enabled) function reference operation amplifier voltage of OPA211. efficientThe high level will disable the computing amplifier. Effective high voltage is defined as the (V+)-0.35 V of the positive pole power supplied to the stop selling. Effective low voltage is defined as (V+)-3V at the feet of the positive power supply. For example, when the VCC is ± 15 V, the device starts at 12 V or below. The device is disabled at 14.65 V or above. If you use a dual power supply or split power supply, you should pay attention to ensuring effective high input or effective low input signals correctly refer to the positive power supply voltage. This pin must be connected to an effective high or low voltage or driver instead of leaving a way. Enable and disable time are provided in the ""typical features"" section (see Figure 39 to 41). When disabled, the output assumes a high impedance state.

Excessive electrical stress

Designers often ask the capabilities of the operation amplifier to withstand excessive electrical stability. These problems are often concentrated on the device input, but may involve the power supply voltage pins and even output pins. Each different pins function has the electrical stability limit determined by the voltage breakdown characteristics of a specific semiconductor manufacturing process and a specific circuit connected to the pin. In addition, internal electrostatic discharge (ESD) is protected in these circuits to prevent an ESD incident that occurs before and in the process of product assembly.

It helps better understand the correlation between this basic ESD circuit and its electrical excessive stress events. Figure 47 shows the ESD circuit contained in OPA211 (represented by the dotted line area). The ESD protection circuit includes several current control diode. These diode connect from the input and output pins and return to the internal power cord, where they encounter large instruments at the internal absorption device. This protective circuit remains inactive during the operation of the normal circuit.

The ESD event generates a pulse with a short duration and high voltage. When it discharge through semiconductor devices, the pulse is converted into a pulse with a short duration and large current. The ESD protective circuit design is used to provide a current circulation around the core of the computing amplifier to prevent it from being damaged. The energy absorbed by the protective circuit was subsequently lost in the form of heat.

When one ESD voltage is formed on the pin of two or more amplifiers, the current flows over one or more to the diode. According to the path of the current, the absorption device may be activated. The trigger voltage or threshold voltage of the absorption device is higher than the normal operating voltage of OPA211, but it is lower than that of the breakdown voltage level of the device. Once this threshold is exceeded, the absorption device will start quickly and keep the voltage on the power rail at the level of safety.

When the operational amplifier is connected to the circuit shown in Figure 47, the ESD protection component will maintain a non -activity state and will not participate in the operation of the application circuit. However, when the external voltage exceeds the operating voltage range of the given pin, this may occur. If this happens, there will be some internal ESD protective circuits that may be biased and transmit current risksEssence Any current is generated by guiding the diode path, rarely involved an absorption device.

FIG. 47 describes a specific example, where the input voltage (VIN) exceeds the positive power voltage (+vs) 500 MV or more. Most of the situations in the circuit depends on the power characteristics. If VS can absorb the current, one in the upper input to the diode to guide the current to the higher and higher and the over -vehicle recognition number (VIN), and the current level may become higher and higher. Therefore, the data table specifications are recommended to limit the input current to 10 mAh.

If the power supply cannot absorb the current, VIN can start to provide the current to the computing amplifier, and then take over as a positive power supply voltage source. The risk in this case is that the voltage may rise to the level that exceeds the absolute maximum rated value of the operation amplifier. In extreme but rare cases, the absorption device is triggered when using VS and -vs. If this incident occurs, the DC path is established between VS and -VS power. The power consumption of the absorption device is quickly exceeded, and the extreme internal heating will destroy the operational amplifier.

Another common problem is that when the power supply vs and/or -vs are 0 V, if the input signal is applied to the input, what will happen to the amplifier. Similarly, this depends on the power characteristics, and the power supply voltage is 0 V, or the level of the amplitude below the input signal amplitude. If the power supply is displayed as high impedance, the power supply current of the computing amplifier can be provided by the input source through the current control. This state is not a normal partial pressure state; the amplifier is likely to not work properly. If the power impedance is low, the current to the diode may become quite high. The current level depends on the capacity of the input source transmission current and any resistance in the input path.

DFN package

OPA211 is provided in the DFN-8 package (also known as SON). DFN packaging is a QFN packaging, which is only located on both sides of the bottom of the packaging. This lead -free packaging has expanded the circuit board space to the maximum extent, and enhances thermal characteristics and electrical characteristics through a bare pad.

DFN package is very small in physical, the route area is smaller, the thermal performance is improved, and the performance of the electrical performance has also been improved. In addition, there is no external lead to eliminate the problem of bending.

DFN packaging can be easily installed with standard printing circuit board (PCB) assembly technology.

The exposed lead frame mold pad at the bottom of the packaging must be connected to V -. Welding hot pads can improve heat dissipation capacity and achieve specific equipment performance.

DFN layout guide

DFN packaged naked lead framework mold pads should be welded on the hot pads on the PCB. At the end of this data table, there is a mechanical chart of the display layout example. According to the requirements of the assembly process, the layout may be improved. At the end of this dataThe mechanical drawings of the tail list the physical size of the packaging and pads.The five holes in the platform pattern are optional, which is used to connect the radiating pores of the leading frame of the lead frame and the PCB heat sink area.

In the process of temperature circulation, keys, wraps, and similar board -level, welded pads of exposed exposure significantly improved board -level reliability tests.Even for low -power applications, bare pads must be welded to PCB to provide structural integrity and long -term reliability.