Features

● Extremely low noise: 10kHz at 4.5NV/√Hz

● Quick stability Time:

● Precision instrument

● Fast fast Data collection

● DAC output amplifier

● Optical electronics

● Sound, ultrasound

● High impedance sensor current

● High -performance audio circuit

● Active filter

Instructions

provides a new computing amplifier's computing accuracy and operational amplifier. Compared with the popular OPA111 computing amplifier, OPA627/637 has lower noise, lower offset voltage and higher speed. It is suitable for extensive scope and high -speed simulation circuits.

OPA627/637 uses high -speed, DIELEC isolation and complementary NPN/PNP process. It works within a wide range of power supply voltage-± 4.5V to ± 18V. The laser fine -tuning DIFET input circuit provides high -precision and low noise performance, which can be comparable to the best bipolar input computing amplifier.

High -frequency complementary transistor allows the increase in circuit bandwidth to achieve dynamic performance that the precision FET computing amplifier cannot achieve in the past. OPA627 is a unified gain and stability. OPA637 stable gain is equal to or greater than 5.

DIFET manufacturing achieves extremely low input bias current without affecting the input voltage noise performance. The low input bias current is kept within a wide range of input co -mode voltage range, and has a unique co -source grid circuit.

OPA627/637 has plastic impregnation, SOIC and metal To-99 packaging. Industrial and military temperature range models are available.

pin configuration

Typical performance curve

Application information OPA627 is a unified gain and stability. OPA637 can be used to achieve higher speed and bandwidth in circuits with no noise gain. Noise gain refers to the closed -loop gain of the circuit, as if the input of non -anti -phase operation amplifiers is driven. For example, OPA637 can be used for non -inverse places with a gain of more than 5 or an inverter bastard with a gain greater than 4.

When selecting OPA627 or OPA637, you must consider the high -frequency noise gain of the circuit configuration. Circuit with feedback capacitors (Figure 1) placed the operation amplifier in the noise gain of high -frequency units. These applications must use OPA627 to obtain appropriate stability. An exception is the circuit in Figure 2, and one of the small feedback capacitors is used to compensate for the input capacitance of the input terminal of the amplifier inverter input. In this case, the closed -loop noise gain and frequency remain constant, so if the closed -loop gain is equal to or greater than 5, the OPA637 can be used.

OPA627/637 is a laser fine -tuning low -dimensional voltage and drift, so many circuits will not require external adjustment. Figure 3 shows the optional connection of the external potential meter to adjust the offset voltage. This adjustment is not used in other places in the compensation system (such as in the later enlarged phase or A/D converter), because this may cause excessive temperature drift. Under normal circumstances, when the offset voltage changes 1MV due to offset adjustment, the offset drift will change about 4 μV/° C (as shown in Figure 3).

Some bipolar operation amplifiers can provide lower voltage noise performance, but voltage noise and bias current noise constitute the system together Total noise. OPA627/637 is unique in providing very low voltage noise and very low current noise. This provides the best noise performance on a wide range of noise sources (including non -meritoric impedance). This can be seen from the performance curve of the source resistance noise and OPA627 noise. Above the source resistance of 2K the source resistance, the operational amplifier will hardly produce additional noise. Below 1K below, the operating amplifier noise occupies the dominant position of the resistor noise, but it has an advantage compared to the precision bipolar computing amplifier.

Circuit layout

Like any high -speed and broadband circuit, careful layout will ensure the best performance. Directly connect to the short distance to avoid bruises, especially at the input pin and feedback circuit.

The shell (only to-99 metal packaging) is connected to the negative electrode power supply because it is connected to most common operational amplifiers. Plastic impregnation, SOIC and TO-99 packaged pin 8 has no internal connection.

The power connection should be bypass with a good high -frequency electrical container near the transportation amplifier pins. In most cases, 0.1 μF ceramic capacitors are enough. OPA627/637 has the ability to high output current (more than 45mA). Applications with low impedance loads or capacitance loads with fast transient signals require power supply to provide large currents. Big bypass containers, such as 1 μF solid cavity capacitors, can improve dynamic performance in these applications.

Input bias current The DIFET manufacturing of OPA627/637 provides a very low input bias current. Because FET's grid current turns around every 10 ° C, in order to achieve the lowest input bias current, the chip temperature should be as low as possible. Therefore, the higher the temperature of the chip 627/637, the higher the static temperature. A simple piercing radiator, such as the Burr Brown model 807HS (to-99 metal packaging), can reduce the chip temperature by about 15 ° C, and reduce the IB to one-third of its preheat value. The 807HS radiator can also reduce the low -frequency voltage noise caused by the airflow and thermal power effect. See the data table of 807HS for details.

By welding the device to the circuit board, the temperature ascending of plastic immersion and SOIC packaging can be minimized. Wide copper traces also help heat dissipation.

OPA627/637 can also work at a reduced power supply voltage to minimize power consumption and temperature rise. In the case of 1B/15V ± 5V, the power of 1/3 ± 5V of the package can reduce the power of 1/3 to 15V ± 5V.

The leakage current between the printing circuit traces is easy to exceed the input bias current of OPA627/637. The ""protection"" mode of the circuit board (Figure 4) reduces the impact of leakage. By connecting the critical high impedance input circuit and the low impedance circuit under the same potential, the leakage current will flow to the low impedance node. The shell (only to-99 metal packaging) is connected to -vs inside.

Improper cleaning or current input may also lead to a decrease in current. Pollutants on parts and circuit boards can be removed with cleaning solvents and ionic water. After each cleaning operation, it should be baked at 85 ° C for 30 minutes.

The input bias current of many FET input computing amplifiers changes with the changes in the input voltage. The input level of the common source grid circuit makes the input bias current of OPA627/637 basically maintained as the common modulus voltage changes. This is an ideal choice for precise high input impedance buffer applications.

Phase protection

OPA627/637 has internal phase reversal protection. Many FET input computing amplifiers appear phase reversal when entering the linear co -modular range.When the input voltage is lower than -12V, this is the most common in the non-inverter circuit, resulting in reverse entering the front orbit. The input circuit of OPA627/637 will not cause phase reversal when the co -mode voltage is too large, so the output is limited to the corresponding guide rail.

Output overload

When the input of OPA627/637 is excessively driven, the output voltage of OPA627/637 is restricted between the positive and negative power of the approximate 2.5V of AP. If you drive to the negative switch limit, it will take about 500 nan seconds to recover. When the output is driven to the positive limit, it takes about 6 μs to restore. The output clamp circuit shown in FIG. 5 to improve the output recovery of OPA627. The diode of the inverter input end can prevent the input bias current from decreased.

Like any high -speed computing amplifier, the optimal dynamic performance can be obtained through the minimum capacitor load. Due to the reduction of impedance at a higher frequency, the load capacitance can be easily driven by slow transportation amplifiers, which will lead to poor performance of high -speed computing amplifiers. Seeing the typical curve shows the function of the settlement time and the capacitance load. The lower bandwidth of OPA627 makes it a better choice to drive a large capacity capacitor load. Figure 6 shows a circuit with a very large load capacitor. The bipolar response of this circuit can also be used to greatly limit the system bandwidth. This is usually useful for reducing the full bandwidth system that does not require OPA627.

The input voltage of OPA627/637 is protected between+vs+2V and --vs – 2V. If the input voltage exceeds these limits, the amplifier should be protected. The diode clamps shown in FIG. 7A will prevent the input voltage from falling more than a positive diode voltage drop, which exceeds the range within the safe range of the power supply. If the input source can provide a current that exceeds the maximum positive current of the diode, the series is used to limit the current. Please note that increasing input resistance will increase noise. 1K 4nv/√Hz theoretical theory of the resistor will increase the 4.5nv/√Hz noise (square and square root) of OPA627/637, generate 6nv/√ total noise Hzorz resistance is less than 100 time, time, time, time, time, time, Noise can be ignored.

Protecting the leakage current in the diode will increase the total input bias current of the circuit. The maximum leakage current of the common diode (such as 1N4148) is about 25NA, which is more than 1,000 times larger than the input bias current of OPA627/637. These diode leakage currents are often much lower and may be enough among many applications. The light falling on the protection of the diode will significantly increase the leakage current, so ordinary glass packaging diode should shield the ambient light. As shown in the figure, use the FE connected to the diodeT can achieve very low leaks.2N4117A is specified as 1Pa, and its metal shell will shade the connection.

Sometimes you need to enter protection on the I/V converter of the inverter amplifier (Figure 7B).Although in normal operations, the voltage of the harmony will be close to zero (equal to the offset voltage of the amplifier), but the large input transients may cause the node to exceed the power supply exceeded 2V.In this case, the grounding of the ground pipeline should be used for protection and knot.Even if there is a low voltage in the search and knot, the normal signal diode may have a large leakage current.Because the reverse voltage on these diode is clamped, the signal transistor connected by the diode can be used as a cheap low leakage diode (Figure 7B).