Features

Excellent sound quality

Ultra -low noise: 1.1nv/√Hz

Super Low D deviation: 0.000015%1kHz

High conversion rate: 27V/μs

Broadband width: 40MHz (g u003d+1)

] High Kailing Ring gain: 130db

Uniform gain stability

Low static current: 3.6MA (single), 7.2ma (double)

Rail -to -track output

Wide power supply range: ± 2.25V to ± 18V

123] Application

Professional audio equipment

microphone front placement large

simulation and digital hybrid console

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123] Broadcasting studio equipment

audio testing and measurement

High -end A/V receiver

Instructions OPA1611 (order) and OPA1612 (dual) dual -pole input computing amplifier achieve a very low 1.1NV/√Hz noise density, and the ultra -low distortion at 1kHz is 0.000015%. OPA1611 and OPA1612 provide rail -to -orbit output width within 600 millivolo, and the load is 2K this increases the net air and maximizes the dynamic range. These devices also have high output driving capabilities of ± 30mA.

These devices work within a very wide power supply range from ± 2.25V to ± 18V, and the power supply current of each channel is only 3.6mA. OPA1611 and OPA1612 computing amplifier units have a stable gain, providing good dynamic performance under extensive load conditions.

The characteristic of the dual version is a complete independent circuit, with the lowest interconnection and freedom, even if it is excessively driven or overloaded.

OPA1611 and OPA1612 are packaged in SO-8, which specifies that the temperature is -40 ° C to+85 ° C.

pin configuration (1), NC indicates that there is no internal connection. The pins can keep floating or connected to the (V+) and (V+)Any voltage.

Typical features

TA u003d+25 ° C, vs u003d ± 15V, RL u003d 2K

Application information

OPA1611 and OPA1612 It is an operational amplifier with a stable increase in unit gain and low accuracy; these devices have no output phase reversal. The application of noise or high -impedance power supply requires the indulgence capacitor to closer to the device power supply foot. In most cases, 0.1 μF capacitors are enough. Figure 29 shows the simplified internal schematic diagram of OPA1611.

Working voltage

OPA161X series operational amplifier works in the range of the range of ± 2.25V to ± 18V, while maintaining excellent performance. The OPA161X series can work in the case of the minimum+4.5V between the power supply and the power of+36V between the power supply. However, some applications do not require the same positive and negative output voltage. For the OPA161X series, the power supply voltage does not need to be equal. For example, the positive power supply can be set to+25V, and the negative power supply is set to -5V.

In all cases, the co -mode voltage must be kept within the specified range. In addition, the key parameters are guaranteed within the specified temperature range from TA u003d -40 ° C to+85 ° C. The parameters of working voltage or temperature change are displayed in typical features.

Input protection

As shown in Figure 30, the input terminals of OPA1611 and OPA1612 are protected by back -to -back diode in order to prevent too high motion voltage. 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 enough, the fast slope input signal can make these diode move forward. Typical features Figure 17 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 has no inherent limit, you can use the input series resistor (RI) and/or feedback resistor (RF) to limit the signal input current. The input series resistor reduced the low noise performance of OPA1611 and checked in the noise performance part below. Figure 30 shows the current feedback and 30 when the input terminal is configured with a restricted resistance configuration.

Noise performance

FIG. 31 shows changes in the power supply source resistance of the unit gain configuration (no feedback resistance network, so there is no additional noise contribution). Total circuit noise.

OPA1611 (GBW u003d 40MHz, G u003d+1) shows, and calculate the general circuit noise. The computing amplifier itself provides voltage noise components and current noise components. Voltage noise is usually modified as a part of the bias voltage. The current noise is modeled to the time variable in the input bias current, and the voltage component of the noise is generated with the source resistance reaction. Therefore, the minimum noise computing amplifier of the given application depends on the source impedance. For low -source impedance, current noise can be ignored, and voltage noise usually dominates. The low -voltage noise of the OPA161X series operational amplifier makes it a good choice for the application of power impedance less than 1kΩ.

Formula in FIG. 31 shows the calculation of the general circuit noise. These parameters are as follows:

EN u003d voltage noise

in u003d current噪声

RSu003d源阻抗

ku003d玻尔兹曼常数u003d

Tu003d温度， Unit: Kaishi (K)

Basic noise calculation

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

The resistance part of the source impedance generates the heat noise of proportion to the square root of the resistance. Figure 31 depicts this function. The source impedance is usually fixed; therefore, the choice of op amp and feedback resistance to minimize their contributions to their total noise.

FIG. 32 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

OPA161X series operational amplifier has excellent distortion characteristics. In the audio frequency range of 20Hz to 20kHz, THD+noise is less than 0.00008%(g u003d+1, VO u003d 3VRMS, BW u003d 80kHz) (see Figure 7).

The distortion generated by the OPA1611 series operations amplifier is lower than the measurement limit of many commercial distorter analyzers. However, special test circuits (as shown in Figure 33) can be used to expand the measurement capabilities.

The operational amplifier distortion can be considered as an internal error source, and you can refer to the input. Figure 33 shows transportationThe amplifier distortion is 101 times (or about 40dB) of the distortion that is usually produced by the computing 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 signal and load of the application to the computing amplifier are the same as the traditional feedback without R3. The R3 value should be kept smaller to minimize its impact on distortion measurement.

The effectiveness of this technology can be verified by repeating measurement under high gain and/or high frequency. Among them, distortion is equipped with equipment within the measurement capacity range of testing. Measuring this data table uses the audio precision system dual distortion/noise/noise. The production of the analyzer greatly simplifies the repeated measurement. However, the measurement technology can be executed by manual distortion measuring instruments.

Capacity load

The dynamic characteristics of OPA1611 and OPA1612 have been optimized for common gains, loads and operations. And may lead to peak or oscillation. Therefore, a heavier capacitance load must be separated from output. The easiest way to achieve this isolation is to connect a small resistance (eg, RS is equal to 50Ω) at the output end.

This small series resistance can also prevent excessive power consumption, if the output of the device is shorter. Figure 19 and 20 show the relationship diagram of the small signal super -adjustment and capacitance load of several RS values. For more information about analysis technology and application circuit, please refer to the application announcement AB-028 (Literature Number: SBOA015, you can download it from the Ti website).

(1), please refer to Figure 7 to Figure 12.

Power loss

OPA1611 and OPA1612 series operator can drive 2K load, and the power supply voltage is as high as ± 18V. When working at a high power supply voltage, the internal power consumption increases. Compared with traditional materials, the copper quotation frame structure used by OPA1611 and OPA1612 series operations amplifiers has improved heat dissipation. The layout of the circuit board also helps reduce the temperature rise to the maximum extent. Wide copper traces help heat dissipation as an extra radiator. By welding the device to the circuit board instead of using the socket, the temperature can be further raised to the lowest.

Excessive electrical stress

Designers often ask the capacity of computing amplifiers 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 products from productsESD incidents that occur before and during the assembly.

It helps better understand the correlation between this basic ESD circuit and its electrical excessive stress events. Figure 34 shows the ESD circuit contained in the OPA161X series (represented by the dotted line area). The ESD protection circuit includes several current control diode. These diode connect from the input and output pin and return to the internal power cord. There, they will be placed in the absorption device inside the operating system. This protective circuit remains inactive during the operation of the normal circuit.

The ESD event will generate a high -voltage pulse with a short duration. When it discharge through semiconductor devices, the pulse is converted into a pulse with 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 OPA161X, but it is lower than that of the permeability 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 34, the ESD protection component will maintain a non -activity state without involving surgery in the application circuit. However, when the external voltage exceeds the operating voltage range of the given pin, this may occur. If this happens, there are risks that some internal ESD protection circuits may be biased and transmitted. Any current is generated by guiding the diode path, rarely involved an absorption device.

FIG. 34 describes a specific example, where the input voltage vin exceeds 500 millivolttoons (+vs) or more. Most of the situations in the circuit depends on the power characteristics. If+vs can absorb current, one of the upper input to the diode to guide the current to+and over -to -+with the higher and higher of the vehicle recognition number (VIN), the current level may become higher and higher. Therefore, the data table specifications are recommended to limit the input current to 10mA.

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 will be triggered when+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 power+vs and/or -vs are 0V,What happens if the input signal is applied to the input end.Similarly, this depends on the power characteristics of the level at the level of 0V or lower than the amplitude of the input signal.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.

If the power absorption current is uncertain, you can add an external Qina diode to the power pins, as shown in Figure 34.The Qina voltage must be selected so that the diode will not be turned on during the normal operation.However, its Qina voltage should be low enough to turn on the Qina diode when the power pins start to rise to the level of the safe working power supply voltage level. Application circuit