Features

Rail -to -rail input

Rail output (within 10 mv)

Broadband: 38 MHz

High conversion rate: 22 v/μs

Low noise: 5 nv/√Hz

Low THD+noise: 0.0006%

unified gain stability

miniature packaging

single, double and four roads

Application

Mobile PA control circuit

Drive A/D converter

Video processing

# 8226; Data collection

Process control

Audio processing

Communication

Source filter

Testing equipment

Instructions

OPA350 series rail CMOS operational amplifier is optimized for low voltage and single power operation. Rail -to -rail input and output, low noise (5 nv/√Hz) and high -speed operation (38 MHz, 22 V/μs) make the amplifier the ideal choice of driving sampling modulus converter (A/D). They are also suitable for mobile phone PA control circuits and video processing (75Ω -driven capacity), as well as audio and general applications. Single, double and four versions have the same specifications to achieve the maximum design flexibility.

The OPA350 series uses a single power supply as low as 2.5 volts of power supply. The input -input voltage range can be extended to 300 millivolves below the ground, which is higher than the 300 millivol to the positive power supply. The output voltage swing is within 10 millivolves of the power rail, and the load is 10,000 euros. The characteristics of Shuangu and Four Road are characterized by completely independent circuits to reduce string disturbance and avoid interaction.

single (OPA350) and double (OPA2350) with micro MSOP-8 surface installation, SO-8 surface installation and DIP-8 packaging. Quad (OPA4350) is packaged in SSOP-16 surface installation and SO-14 surface installation that saves space. All prescribed temperature range is 40 ° C to 85 ° C, and the operating temperature is 55 ° C to 150 ° C.

OPAX350 Harmonic distortion

Device information (1)

(1), please refer to the appointment appendix at the end of the data table.

Typical features

Unless otherwise explained, all specifications are connected to VS/2 when all specifications are in TA u003d 25 ° C, vs u003d 5 v, and rl u003d 1 kΩ.

Detailed explanation Overview

] OPA350 series rail -to -track CMOS operational amplifier is optimized for low voltage and single power operation. Rail -to -rail input and output, low noise (5 nv/√Hz) and high -speed operation (38 MHz, 22 V/μs) make the amplifier the ideal choice of driving sampling modulus converter (A/D). They are also suitable for mobile phone PA control circuits and video processing (75Ω -driven capacity), as well as audio and general applications. Single, double and four versions have the same specifications to achieve the maximum design flexibility.

Function box diagram

Feature description

OPA350 series operational amplifier (operation amplifier) u200bu200bis made of the most advanced 0.6 micron CMOS process. They have a stable unit gain and are suitable for extensive common applications. Rail -to -rail input and output make it an ideal choice for driving sampling A/D converter. They also apply to control the output power of the phone. These applications usually require high speed and low noise. In addition, the OPA350 series also provides a low -cost solution for general and consumer video applications (75Ω -driven capabilities).

Excellent communication performance makes the OPA350 series suitable for audio applications. Their bandwidth, conversion rate, low noise (5NV/√Hz), low THD (0.0006%) and small packaging options are ideal options for these applications. The AB -level output level can drive a 600Ω load of any point between V+and the ground.

Rail -to -track input and output width significantly increased the dynamic range, especially in low -voltage power supply applications. Figure 25 shows the input and output waveform of OPA350 in the unit gain configuration. The operation is powered by a 5 volt power supply, and the load of 1,000 Euros is connected to VS/2. The input is 5 VPP sine waves. The output voltage is about 4.95VPP.

The power pins should be bypass with 0.01-μF ceramic capacitors.

Working voltage

OPA350 series operational amplifier is completely specified from 2.7 V to 5.5 V. The power supply voltage range is 2.5 V to 5.5 V. Test the parameter within the specified power supply range: ThisIt is a feature of the OPA350 series. In addition, many specifications are suitable for 40 ° C to 85 ° C. Without the entire working voltage range, most of the performance remains almost unchanged. Parameters with significant changes in working voltage or temperature are typical.

Rail -to -rail input

The test input input co -mode voltage range of the OPA350 series exceeds 100 millivolves of the power rail. This is achieved through a complementary input level: an N channel input difference is parallel parallel parallel with a PChannel differential, as shown in Figure 26. For the input voltage near the track, the N channel is valid, usually above the (V+)-1.8 V to 100 MV above the positive pole power, and the P channel is to about 100 MV below the negative power supply to approximately (V+) -1.8 V. The input voltage is turned on. There is a small transition area, usually (V+) -2 V to (V+) -1.6 V, and the two voltage pairs are opening in this transition area. The 400 MV transition area can change ± 400 MV with the process. Therefore, in the low-end, the range of the transition zone (both input levels open) is (V+)-2.4V to (V+)-2V, and the high-end maximum (V+) -1.6V to (V+)-1.2V.

OPA350 series operational amplifier uses laser fine -tuning to reduce the deviation voltage difference between the N -channel and the P channel input level, thereby improving the co -size suppression capacity, and in N N Channel pairs and P channel pairs smoothly transition. However, in the 400 MV transition zone, PSRR, CMRR, offset voltage, offset drift, and THD may be reduced compared with the operation outside the area.

Dual -folding the common source code of the common source of the two input pairs adds a differential signal to the AB output stage. Generally, the input bias current is about 500fa. However, the large input (exceeding 300 millivoltors exceeding the power rail) will turn on the input protection diode, causing excessive current inflow or outflow input pins. If the current on the input pin is limited to 10 mAh, it can tolerate an instantaneous voltage of 300 millivoltors exceeding the power supply. This is easy to achieve through the input resistance, as shown in Figure 27. Many input signals are limited to less than 10 mAh; therefore, there is no need to limit the resistor.

The output of the rail

The output stage of the AB class uses a common source transistor to achieve rail transmission. For light resistance loads ( gt; 10 kΩ), the output voltage swing is usually 10 millivolves of the power rail. Under the heavier resistance load (600Ω to 10 kΩ), the output can swing from the power rail to within dozens of millivoltta, and maintain a high -opening increasing gain. For more information, see Figure 17 and Figure 18.

Capacity load and stability

OPA350 series operational amplifier canDrive various capacitance loads. However, in some cases, all operational amplifiers may become unstable. The configuration, gain, and load value of the operation amplifier are only a few factors to consider when determining the stability. The computing amplifier of the unit gain structure is the most vulnerable to inclusive load. The output impedance of the capacitance load and the operational amplifier and any additional load resistance react, and a polar point is generated in the small signal response to reduce the phase margin.

In terms of unit gain, the OPA350 series operational amplifier performed well under the large capacitor load. Increasing gain can enhance the capacity of the amplifier to drive more capacitors. Figure 21 shows the performance of the 1-kΩ resistor load. Increasing load resistance can improve capacitor load driving capacity.

Drive A/D converter

OPA350 series operational amplifier is optimized for driving medium -speed (up to 500kHz) samples A/D converter, and also provides higher -speed converters with higher -speed converters Excellent performance. The OPA350 series provides an effective method to buffer the input capacitance of A/D and inject the charge generated by it, and at the same time provides signal gain.

FIG. 28 shows OPA350 Drive ADS7861. ADS7861 is a dual 500 KHz 12-bit sampling converter in a small SSOP-24 package. When used with the micro -packaging options of the OPA350 series, this combination is an ideal choice for limited space applications. For more information, see the ADS7861 data table, dual, 500KSPS, 12 -bit, 2+2 channels, synchronous sampling modulus converter (SBAS110).

Output impedance

OPA350's common source output -level low -frequency opening output impedance is about 1kΩ. When the operational amplifier is connected to the feedback, this value will be significantly reduced by the loop gain of the computing amplifier. For example, when the opening gain is 122DB, the output impedance under unit gain is reduced to less than 0.001Ω. Every 10 years when the closed -loop gain increases, the loop gain will reduce the same amount, resulting in an increased increase in effective output impedance by 10 times (see Figure 15).

At a higher frequency, the output impedance rises with the decline of the operating increasing increase in the operation amplifier. However, at these frequencies, the output becomes capacitance due to parasitic capacitors. This can prevent excessive output impedance, which may cause stability problems when driving capacitance loads. OPA350 has excellent capacitor load driving capabilities and can be used to calculate the bandwidth of the amplifier.

Device function mode

OPAX350 has a single function mode. When the power supply voltage is greater than 2.7 v (± 1.35 V)), it can work. The maximum power supply voltage of OPAX350 is 5.5V (± 2.75V).

Application and implementation

Note

The information in the following chapters is not part of the TI component specification, TI does not guarantee its accuracy or integrity. TI's customers are responsible for determining the applicability of the component. Customers should verify and test their design implementation to confirm the system function.

Application information

Low -pass filter is usually used in signal processing applications to reduce noise and prevent confusion. OPAX350 is an ideal choice for building high -speed, high -precision active filters. Figure 29 illustrates the common second -order low -pass filter in signal processing applications.

Typical application

Second -order low -pass filter

Design requirements

Use the following in this design example. Parameters:

gain u003d 5 v/v (reverse gain).

Low -pass cutting frequency u003d 25 kHz.

the second-order cutting than the snowfoff filter, the peak value of the internal gain is 3-DB.

Detailed design program

The infinite gain multi -feedback circuit of the low -pass network function is shown in the same formula. Use Formula 2 to calculate the voltage transmission function.

This circuit generates a signal reversal. For this circuit, DC gain and low -pass dead frequency can be calculated in formula 2.

Software tools can easily simplify the design of the filter. Webench #174; Filter Designer is a simple, powerful and easy -to -use active filter design program. Webench filter design allows you to use TI supplier partners's TI computing amplifiers and passive components to create optimized filter design. Webench #174; Filter Designer is a web -based tool provided by Webench #174; Design Center. It allows you to design, optimize and simulate a complete multi -level active filter solution in a few minutes.

Application curve

Single -power video line drive

Figure 31 shows the single power supply G u003d 2 composite video line driver Circuit. The synchronous output of the composite video cable extends to the ground. As shown in the figure, the input of the computing amplifier should be coupled and co -displaced to provide sufficient signal distribution amplitude to consider these negative signals in the configuration of the single power supply.

A 75Ω resistor is connected to the input terminal, and it is coupled with 47μF capacitors to the pressure division. Figure 3In 1, the point is about (v )+1.7 V. To set the best bias point, you need to understand the nature of the composite video signal. In order to obtain the best performance and avoid distortion caused by the transition zone of the OPA350 complementary input level. See the discussion between the rail input between the rail input.

Increase the feedback capacitor to improve the response

In order to obtain the optimal stability and stability of the high impedance feedback network, it may need to be on the feedback resistor RF RF Add feedback capacitors, as shown in Figure 32. The capacitor compensation is produced by the feedback network impedance and the input capacitor (and any parasitic layout capacitance) of the OPA350. This effect becomes more significant in high impedance networks.

Feedback capacitors can use variable capacitors, because input capacitors may change between the computing amplifier, and the layout capacitance is difficult to determine. For the circuit shown in FIG. 32, the value of the variable feedback capacitors should be selected to make the input resistance multiplied by the input capacitance (usually 9 PF) of the OPA350 plus estimated parasitic layout capacitance. ]

Among them:

CIN is equal to the input capacitance of OPA350 (the sum of differentials and co -mode) of OPA350 plus layout capacitors.

The capacitor can be changed until the best performance.

The dual -transportation instrument amplifier that improves high -frequency co -mode inhibitory

OPAX350 is very suitable for high input impedance applications, such as instrument amplifiers. The configuration of the two amplifiers shown in FIG. 33 Rejects any co -mode signals, and sensing the small differential input voltage generated by the resistance bridge. When the differential signal generated by the bridge is zero, the voltage benchmark sets the output to 2.5 V. OPAX350's high co -model suppression and frequency response, inhibitory and co -model noise may be coupled from the bridge incentive source to the bridge circuit. According to the equal formula shown in FIG. 33, the gain of the circuit by RG is determined.

10 KHz high -pass filter

High -pass filter is used to inhibit DC signals and low -frequency changes in the low frequency, such as the relationship between drift and temperature. FIG. 34 shows a high -pass filter with a 10 -kHz low -frequency cut -off frequency.

Power suggestion

OPAX350 is stipulated at 2.7 v to 5.5 v (± 1.35 v to ± 2.75 v); many specifications are suitable for -40 ° to -40 ° C to 85 ° C. In typical features, parameters that can show significant changes related to working voltage or temperature.

Layout

layout guide

To obtain the best operating performance of the equipment,Please use a good PCB layout practice, including:

noise can be transmitted to the analog circuit through the power pins and calculation amplifiers itself through the entire circuit. The barrier container is used to reduce the coupling noise by providing a low -impedance power supply of an analog circuit.

-Colin the low ESR and 0.1-μF ceramic side electric container between each power supply foot and ground, and as close to the device as much as possible. Single -width capacitors from V+to the ground are suitable for single power applications.

Circuit simulation and the individual grounding of the digital part are one of the simplest and most effective noise suppression methods. A layer or multi -layer on the multi -layer printing circuit board is usually used for ground layers. The floor helps to distribute heat and reduce the noise of electromagnetic interference. Ensure that the number of numbers and simulation of the ground is separated, and the flowing current flows. For details, see the circuit board layout technology (Sloa089).

In order to reduce parasitic coupling, the input trajectory should be as far away from the power supply or output trajectory as much as possible. If these record channels cannot be separated, it is much better than parallel to the noise recorder.

The external components are as close to the device as possible. As shown in Figure 35, keeping RF and RG approaching inverter inputs can minimize parasitic capacitors.

The length of the input record should be as short as possible. Always remember that the input trajectory is the most sensitive part of the circuit.

Consider setting a driver's low impedance protection ring around the key line. The protective ring can significantly reduce the leakage current of different potentials nearby.

It is recommended to clean the PCB after assembly to obtain the best performance.

Any precision set circuit may change performance changes due to water entering plastic packaging. After any water -based PCB cleaning process, it is recommended to bake PCB components to remove the water packaging water during the cleaning process. In most cases, it is enough to bake for 30 minutes after low temperature at 85 ° C.

layout example