Features

● Low power: 50MW/Chan.

● Stable unit gain bandwidth: 360MHz

● Fast settlement time: 20ns to 0.01%

● Low harmonic: 5MHz at -77dbc

● Differential gain/phase error: 0.01%/0.025 °

● High -output current: 85ma

Amplifier

● CCD imaging amplifier

● Ultrasonic signal processing

● ADC/DAC gain amplifier

● Active filter

● High -speed integral device

● Differential amplifier

Instructions

OPA2650 is a dual, low power consumption, broadband voltage feedback amplifier. It has a high bandwidth of 360MHz and a 12 -bit stable time of only 20NS. Low distortion allows it to be used in communication applications, and broadband and real differential input levels make it applicable to various active filter applications. Its low distortion provides excellent performance for telecommunications, medical imaging and video applications.

OPA2650 internal compensation for unified gain stability. Due to its ""classic"" computing amplifier circuit structure, the amplifier has completely symmetrical differential input. Its unusual combination of speed, accuracy and low power consumption make it a prominent choice for many portable, multi -channel and other high -speed applications. In these applications, the power is very high.

OPA2650 also offers single (OPA650) and four (OPA650) configurations.

Note: Only half of OPA2650 is displayed in the figure.

Typical performance curve

Unless otherwise explained, other ta u003d+25 ° C, vs u003d ± 5V, RL u003d 100 , RFB u003d 402 When the gain is +1, RFB u003d 25 .

Application information Performance discussion OPA2650 is a dual low power consumption, broadband voltage feedback amplifier. Each channel has internal compensation to provide unit gain stability. The voltage feedback structure of OPA2650 has real differences and completely symmetrical inputs. This minimizes the offset error, making OPA2650 very suitable for the filter and instrumentDesign. As a dual -computing amplifier, OPA2650 is an ideal choice. In the design of multiple channels to reduce board space, power consumption and cost are the key. Its communication performance is optimized and can provide 160MHz gain bandwidth accumulation and fast 0.1%stable time of 11ns. This is an important consideration in high -speed data conversion applications. Due to its excellent settlement characteristics, the low -DC input offset of ± 1MV and the drift support high -precision requirements of the drift of ± 3 μV/° C. In applications that require higher conversion rates and broader bandwidth, such as video and high -bit rate digital communication, consider dual current feedback OPA2658.

Circuit layout and basic operations

To obtain the best performance and high -frequency amplifier, such as OPA2650 needs to pay close attention to the selection of layout parasites and external components. Suggestions for PC plate layout and component selection include:

A), minimize parasitic capacitors to minimize all signal input/output pins. Parasitic capacitors on the output and reverse input terminals will cause unstable; at non -switching inputs, parasitic capacitors will react with the source impedance, resulting in unintentional bandwidth limit. To reduce unnecessary capacitors, the window around the signal input/output pin should be opened on all ground and power plane. Otherwise, the ground and power aircraft should remain complete elsewhere.

B), shortening distance ( lt; 0.25 "") from two power supply to high -frequency 0.1 μF decoupled capacitor. At the foot, grounding and power plane layout should not be close to the signal input/output tube Foot. Avoid narrow power and ground traces to minimize the inductance between the pin and the decoupling capacitor. It should also use a larger (2.2 μF to 6.8 μF) decoupled capacitor, which is valid at a lower frequency. These can Place in a place where the device is slightly far away, and it can be shared between multiple devices in the same area of u200bu200bthe PC board.

C), carefully select and place the external component will maintain the high -frequency performance of OPA2650. The resistance. The resistance. The device should be a very low type of electricity resistance. The surface paste resistance is the best and allows a more compact overall layout. Metal film or carbon component axial leading resistance can also provide good high -frequency performance. Similarly, their clues are allowed As short as possible. Do not use a wire winding resistor in high -frequency applications.

Because the output pins and inverter input pins are most sensitive to parasitic capacitors, they will always feedback and series output resistors ( If so), as far as possible to the packaging pin. Other network components, if the non -converting input terminal is connected to the resistor, should also be placed near the packaging place.

Even if the low parasitic capacitor diversion resistor, the high resistance resistance is too high. Value will also generate significant time constant and reduce performance. Good metal membranes or surface paste resistors are about 0.2pf when parallel. Extreme/or zero, which may affect electricityThe operation of the road. Keep the resistance value as low as possible to meet the consideration of the output load. 402 #8486 for typical performance charts; feedback is a good design starting point. Note that for unit gain followers, it is recommended to use 25 feedback resistance instead of direct short circuit. This effectively reduces the Q value of parasitic inductance (feedback line) at the inverter input terminal.

D), a short direct trace line or transmission line can be transmitted on the connecting board with other broadband devices. For short connections, the input of tracking and to the next device is considered as a concentrated capacitor load. A relatively wide trace line (50 to 100 dense ears) should be used, and it is best to open the ground and power aircraft around it. It is estimated that the total capacitance load is estimated, and RISO is set according to the recommended RISO and the curve of the capacitance load. Low parasitic loads may not require RISO, because OPA2650 is named in name, and can work under the 2PF parasitic load.

If a long record of recorded and the inherent 6DB signal loss of the double -end transmission line is acceptable, the use of micro -band lines or lines to achieve the matching impedance transmission line (see the ECL micro -zone and band belt and the belt Symptom layout technology design manual). The environment does not require 50 in fact, a higher impedance environment will improve distortion, such as distortion and load curve charts. Define the characteristic impedance according to the circuit board material and the required trace line size definition, use the matching series resistor at the output end of the amplifier, and use the end parallel resistor to the input terminal of the target device. It should also be remembered that terminal impedance will be a parallel combination of parallel resistance and target equipment input impedance; the total effective impedance should be matched with the tracking impedance. Multiple destination devices are best handled as a separate transmission line, each with its own series and parallel ending.

If the 6DB attenuation loss of the double -end line line is unacceptable, the long record can only be terminated in series at the source end. This will help isolate line capacitors from the op amp, but it will not maintain signal integrity and two -terminal lines. If the parallel resistance of the destination end is limited, the sterilization of the string and parallel impedance will generate a certain signal attenuation.

E), for high -speed parts such as OPA2650, sockets are not recommended. The additional lead length and the capacitance of the pipes introduced by the socket have produced a very troublesome parasitic network, which is almost impossible to achieve smooth and stable response. Welding parts to the circuit board can get the best results. If you need DIP packaging sockets, high -frequency buried insertions (such as McKenzie Technologies#710C) can produce good results.

Power voltage

OPA2650 usually stipulates that ± 5V power supply is used. The 10%tolerance of the power supply, or the ECL – 5.2V of the negative electrode power supply, is within the maximum of 11V. The total power supply voltage range. A higher power supply voltage may destroy the internal connection and may cause disaster failure. As long as the common modulus voltage restrictions,Single power operation is possible. Common mode input and output voltage specifications can be interpreted as the required power supply voltage balance. Observing this input and output net empty requirements will allow non -standard or single power operations. Figure 1 shows a single supply operation method.

Disposal voltage adjustment

If you need additional offset adjustment, you can use the circuit in Figure 2 instead of reducing the offset volume. Changes in temperature. Avoid external adjustments as much as possible, because external noise, such as power noise, may accidentally couple into the reverse input end of the amplifier. Remember, the additional offset error can be generated by the input bias current of the amplifier. Two input impedances are matched as possible, as shown in R3. This will reduce the output offset voltage caused by the input offset current of the amplifier.

ESD protection

ESD damage has been well recognized for MOSFET devices, but any semiconductor device is vulnerable to this potential source of destruction Impact. This is especially true for very high -speed and fine geometric processes.

ESD damage can cause subtle changes in the input characteristics of the amplifier without having to damage the device. In the precision operational amplifier, this may lead to a significant decrease in offset voltage and drift. Therefore, when dealing with OPA2650, it is strongly recommended to take ESD treatment prevention measures.

Output driving capacity

OPA2650 is optimized to drive 75 and 100 #8486. This device can drive 2VP-P into 75 load. This high output driver capacity makes OPA2650 an ideal choice for extensive radio frequency, intermediate frequency and video applications. In many cases, no additional buffer is needed.

Many high -speed applications, such as the drive A/D converter, require the computing amplifier of low broadband output impedance. For example, when the signal -related capacitance of the input terminal of the driver Flash A/D converter, low output impedance is essential. As shown in Figure 3, OPA2650 maintains a very low closed -loop output impedance in the frequency. Closed -loop output impedance increases with frequency, because the frequency of the loop gain decreases.

Thermal factors

OPA2650 does not require heat dissipation under most operating conditions. The maximum expectation will set the maximum allowable internal power consumption as described below. In any case, the highest knot temperature must not exceed 175 ° C.

Total internal power consumption (PD) is the sum of the additional power consumed by static power (PDQ) and two output (PDL1 and PDL2) when transmitting load power. Static power is the total power supply voltage of the specified air supply current by the two channels. PDL1 and PDL2 will decideIn the required output signal and load. For the ground resistance load and equal dual -polarity power supply, when the output is fixed at a voltage equivalent to the 1/2 power supply voltage, they will reach the maximum value. Under this condition, PDL1 u003d vs2/(4 #8226; RL1), where RL1 includes feedback network load. The calculation method of PDL2 is the same.

Note that the power consumption of the internal power is the output level, not the load.

The working knot temperature (TJ) is given by TA+PDθJA, of which TA is the ambient temperature.

For example, the maximum TJ of OPA2650U, the two of which are g u003d+2, RL u003d 100 , RFB u003d 402 TA u003d+85 ° C.

This can be obtained:

Capacity load

OPA2650 output level has been optimized to drive low resistance loads. However, capacitive loads reduce the phase habits of the amplifier, which may cause high -frequency peak or oscillation. The capacitance load greater than 10PF should be isolated by connecting a small resistance (usually 15 to 30 ) with the output shown in Figure 4. This is especially important when driving high -capacitor loads (such as flash memory A/D converters). Increasing gain from +1 will improve the capacitance load driving because the phase of the phase increases.

Generally speaking, the capacitance load should minimize to obtain the best high -frequency performance. If the cable is connected correctly, the coaxial cable can be driven. When the coaxial cable or transmission line is connected to the inner end of its characteristic impedance, the capacitor (RG-58 is 29pf/feet) of the coaxial cable does not load the amplifier.

Frequency response compensation

Each channel of OPA2650 has been internal compensation to stabilize at the unit gain, and it has a nominal 60 ° phase. This is very suitable for broadband integrator and buffer applications. The flatness and frequency response flat degree will be improved at higher gain. Recall that the reverse gain-1 is equal to the bandwidth gain +2, that is, noise gain u003d 2. The external compensation technology of the voltage feedback computing amplifier can be applied to the device. For example, in a non -counter -phase configuration, the capacitor is placed on the feedback resistor to reduce the gain from f u003d (1/2πrfcf) to +1. Alternatively, in the reversal configuration, you can limit the bandwidth without modifying the reversal gain by putting the ground on the RC network on the reversal node. This has the effect of increasing noise gain in the high -frequency place, thereby restricting the bandwidth of the input signal through the gain bandwidth.

Under a higher gain, the gain bandwidth of the voltage feedback topology will restrict the bandwidth according to the opening frequency response curve. For applications that require wider band wide and higher gain, considerDual current feedback model OPA2658. In applications that require large feedback resistors (such as optoelectronic diode cross -resistant circuits), preventive measures must be taken to avoid the peak of gain due to the polar point formed by the feedback resistance and the polar point of the input of the input. This pole can be compensated by connecting a small capacitor and feedback resistance to generate a zero item. In other high -gain applications, the use of a three -resistor ""T"" connection will reduce the feedback network impedance, which reacts with the parasitic capacitance at the harmonious node.

Pulse stability time

High -speed amplifiers like OPA2650 can achieve extremely fast stable time under pulse input. In order to obtain the best stable time, a good frequency response response flat and phase linearity is required. As shown in the specification table, when the gain is +1, the stable time of the 2V jump of OPA2650 is very fast. The specification is defined as the time required for stability in the specified error zone around its final value after the input is defined. For 2V steps, 1%settlement corresponds to the error band of ± 20mv, 0.1%is corresponding to ± 2mv error band, and 0.01%is corresponding to ± 0.2mv error band. In order to obtain the best stable time, especially in the ADC capacitance load, the peak value of frequency response can be small or no. Recommended RISOs for capacitance loads will limit this peak and reduce settlement time. The rapid and fine scale setting (0.01%) needs to pay close attention to the grounding background in the power supply counter -coupling capacitor. In order to obtain the highest performance, OPA642 can be considered, which provides a very high open -loop DC gain.

Licoar gain and phase

Differential gain (DG) and differential phase (DP) are one of the more important indicators in video applications.

The percentage change of the specific change of the closed -loop gain relative to the output voltage level is defined as DG. DP is defined as a closed -loop phase in the same output voltage change. Both DG and DP are specified at the NTSC sub -wave frequency of 3.58MHz. DG and DP increase the closed -loop gain and output voltage conversion. All measurement uses the Tektronix model VM700 video measurement device.

Twisted

OPA2650 The relationship between the harmonic distortion characteristics and frequency and power output of OPA2650 in the load is displayed in the typical performance curve. As shown in Figure 5, it can significantly improve deformation by increasing the load resistance. When calculating the valid load resistance that the amplifier sees, remember the contribution of the feedback resistance.

String

Stringing is the result of a signal of one channel with the output signal of another channel and the result of self -copy in the output of another channel. String occurs in most multi -channel integrated circuits. In the dual device, the effect of the stringing disturbance is to drive a passage and observe that it is not driven at different frequenciesThe channel output is measured. The size of this influence is used as a reference between the string of channels and is expressed in decibels. ""Entering reference"" refers to the direct correlation between gains and skewers. Therefore, when the gain increases, the skewers will also increase the same factors that are equal to gain. Figure 6 shows the measuring string effect in OPA2650U.

Spice Model

When analyzing the performance of simulated circuits and systems, it is very useful to use SPICE to computer simulation on circuit performance. This is especially true for video and RF amplifier circuits, because parasitic capacitors and inductors will have a significant impact on circuit performance. The SPICE model can be obtained from the disk of the Burr Brown application department.

Demonstration board

Each OPA2650 packaging style has a display board. These circuit boards implement a very low parasitic layout, which will produce excellent frequency and pulse response shown in typical performance curves. For each packaging style, the recommended demonstration boards are:

Please contact your local Burr Brown sales office or dealer to order the demonstration board.

Typical application