Features

● gt; 1MHz cross -resistance bandwidth

Good long -term VOS stability

] ● Bias current: 50Pa (maximum)

● offset voltage: 25 μV (maximum)

● Dynamic range: 4 to 50 years

● Drift: 0.1 μV/° C (maximum value)

●

gain bandwidth: 90MHz

]

● Static current: 7.5ma

● Power range: 2.7V to 5.5V

● single and dual duality Version

●

Micro packaging: MSOP-8 Application

●

Optical diode monitoring

[ 123] ● Precision I/V conversion

● Vicential Playing instrument

● Cat-SCANNer front end

Explanation

The OPA380 series spans provides high -speed (90MHz gain bandwidth [GBW]) operation, which has high accuracy, excellent long -term stability and very low 1/F noise. It is an ideal choice for high -speed photoelectric diode applications. OPA380 has a bias voltage of 25 μV, a bias current of 0.1 μV/° C, and a bias current of 50Pa. OPA380 far exceeds the offset, drift and noise performance provided by the traditional JFET computing amplifier.

The signal bandwidth of cross -blocking large device depends to a large extent on the GBW of the amplifier, the parasitic capacitance of the photoelectric diode, and the feedback resistor. OPA380's 90MHz GBW can achieve a transmissile bandwidth greater than 1MHz in most configurations. OPA380 is an ideal choice for the fast -control loop of optical fiber power levels.

Due to the high accuracy and low noise characteristics of OPA380, it can achieve a dynamic range of 4 to 50 years. For example, this ability allows measuring 1NA -level signal current in a single I/V conversion level, up to 100 μA. Compared with the number amplifier, the OPA380 provides a very wide bandwidth throughout the dynamic range. By using an external drop-down resistor to -5V, the output voltage range can be extended to 0V.

OPA380 (order) is encapsulated by MSOP-8 and SO-8. OPA2380(Double) Can be used in micro MSOP-8 packaging. The specified temperature range is -40 ° C to+125 ° C.

OPA380 related device

pin allocation — push view

Note: Note: (1) NC means no internal connection.

Typical features: vs u003d+2.7V to+5.5V

Unless otherwise explained, it is in TA u003d+25 ° C, RL u003d 2K And all specifications of vout u003d vs/2.

Application information Basic operation OPA380 is a high -performance cross -blocking large, with very low 1/F noise. Due to its unique structure, OPA380 has good long -term input voltage offset stability, and a 300 -hour life test at 150 ° C indicates that the changes in random distribution are equal to the measurement repetitiveness of 1 μV. The performance of OPA380 comes from the combination of internal automatic zero -mixer and high -speed amplifier. Compared with the traditional composite method, OPA380's circuit design improves overload recovery and stable time. It is specially designed and characterized to adapt to the circuit option to allow 0V output operations (see Figure 3).

OPA380 is used for reversal configuration, and non -reversing input is used as a fixed bias point. Figure 1 shows OPA380 in typical configuration. Power insertion should be bypassed with 1 μF ceramics or 钽 capacitors. It is not recommended to use electrolytic capacitors.

Working voltage

OPA380 series operational amplifier is fully stipulated in the temperature range of 40 ° C to+125 ° C from 2.7V to 5.5V. The parameters that significantly change with the working voltage or temperature are displayed in typical features.

Internal offset correction

The OPA380 series operational amplifier uses an automatic zero top topology, and there is a 90MHz computing amplifier in the signal channel. The amplifier uses a proprietary technology for zero correction per 100 μs. After power -on, the amplifier requires about 400 μs to achieve the specified VOS accuracy, including about 100 μs of a complete automatic zero -zero -zero period and starting time of the bias circuit. Before that, the amplifier will work normally, but the bias voltage is not specified.

This design has almost no mixed and very low noise. Zero campus happens at the frequency of 10kHz, but due to internal filtering, there is almost no basic noise energy at this frequency.quantity. For all actual uses, the energy of any fault is 20 MM or higher, and it is easy to filter, if necessary. Most applications are not sensitive to this high -frequency noise and do not need filtering.

Input voltage

The input co-mode voltage range of the OPA380 series is expanded from V to (V+)-1.8V. When the input signal is higher than this co -mode range, the amplifier will no longer provide effective output values, but it will not be locked or reversed.

Enter overvoltage protection

The device input is protected by the ESD diode. When the input voltage exceeds the power supply voltage of about 500 millivolves, the diode will be turned on. If the current is limited to 10 mA, it can tolerate an instantaneous voltage of 500 millivoltors exceeding the power supply. The characteristics of the OPA380 series are that when the input exceeds the power supply, if the input is a current limit, there is no phase reversal.

Output range

OPA380 is specified in at least 600 millivoltors on orbit and 100 millivoltage negative voltage range, the load is 2K and has good linearity. Swing to the neckline while maintaining a good linearity, it can extend to 0V to see the cross section to achieve the output facing the ground. See the typical characteristic curve, output voltage swing and output current.

The width of OPA380 is slightly closer than the positive track specified;

overload recovery

OPA380 is designed to prevent output saturation. After excessive driving to the right track, it usually only needs 100NS to restore linear operation. The time required for negative load recovery is longer, unless the drop -down resistor connected to a more negative power supply will extend the output swing to the next section to achieve the output swing to the ground.

Implementing output places

Some applications require the output voltage from 0V to the positive standard voltage (such as+4.096V), high accuracy. For most single power op amps, when the output signal is close to 0V and the lower limit of the output of the single power supply is close, there will be problems. A good single power supply amplifier may be swinging near the ground of the single power supply, but it will not reach 0 volts.

OPA380 output can swing to the ground on a power supply, or slightly lower than the ground. This extended output swing needs to use another resistor and an additional negative power supply. A drop -down resistor can be connected between the output end and the negative electrode power supply, and the output end is pulled down to 0V. See Figure 3.

OPA380 has an output stage, allowing the use of this technology to pull the output voltage to its negative power rail. However, this technology is only applicable to the output level of certain types. OPA380 is designed to be availableUse this method very well. The accuracy below 0 volt is very high. Reliable operations can be guaranteed within the specified temperature range.

Partial voltage optoelectronics diode in the single power circuit

When the photoelectric diode is not exposed to any light, the+in input can be biased out of the output voltage with a positive and direct current voltage, and allows the amplifier output to output Instructed the real zero -optical diode measurement. It can also prevent additional delays due to corruption. This partial pressure appears on the photoelectric diode, which provides reverse bias for faster operations. The RC filter placed at this partial pressure point will reduce noise, as shown in Figure 4. The bias voltage can also be used as a offset bias point for the ADC that does not include ground.

Cross -blocking large weapon

Broadband width, low input bias current, low input voltage and current noise make OPA380 the ideal broadband photovoltaic diode cross -blocking large weapon Essence Low -voltage noise is important because the optical diode capacitance increases the effective noise gain of the circuit at high frequency.

The key elements of cross -resistance design are shown in Figure 5:

Total input capacitance (CTOT), which is used by photoresal diode capacitors (CD diode) OPA380 is 3pf+1.1pf);

The expected transmissions (RF);

OPA380 (90MHz) gain bandwidth (GBW).

By setting up these three variables, feedback capacitance (CF) can be set to control the frequency response .cstray is the biased capacitance of RF. For typical surface stickers, it is 0.2PF.

In order to obtain the largest flat second -order Bartworth frequency response, the feedback pole should be set to:

The bandwidth calculation formula is as follows:

]

These equations will lead to the maximum cross -guided bandwidth. For higher cross -resistance bandwidth, you can use high -speed CMOS OPA300 (SBOS271 (180MHZGBW)) or OPA656 (SBOS196 (230MHZGBW)).

For more information, see the application announcement AB 050 (SBOA055), and intuitively compensate the cross -block.

Figure 5: Cross -resistance large weapon

Note: (1) CF is optional to prevent the peak of gain.

(2) CSTRAY is a messy capacitor of RF (the surface installation resistor is usually 0.2PF).

(3) CTOT is an optoelectronic diode capacitor plus OPA380 input capacitance.

Cross -resistance bandwidth and noise

Limiting the gain of radio frequency settings can reduce the noise circuit of the cross -guided output place. However, all required gains should occur in cross -resistance, because increasing gains after cross -blocking large vessels usually generate poor noise performance. The noise spectral density generated by radio frequency increased with the increase in the square RF square root, while the signal increased linearly. Therefore, when all required gains are placed in cross -resistance, the signal -to -noise ratio is increased.

Total noise increases with the increase of bandwidth. Limit the circuit bandwidth within the required range. Use a capacitor CF on the feedback resistor RF to limit the bandwidth, even if you consider the total output noise, you do not require stability.

FIG. 6A shows a cross -resistant circuit without feedback capacitors. The cross -resistance gain generated by this circuit is shown in Figure 7. -3DB points are about 10MHz. Added a 16PF feedback capacitor (Figure 6B) will limit the bandwidth and generate -3DB points at about 1MHz (see Figure 7). Create the second pole (Figure 6C) by adding a filter (RFILTER and CFILTER) to further reduce the output noise. The second pole is placed in the feedback loop to maintain the low output impedance of the amplifier. (If the magnetic pole is placed outside the feedback loop, an additional buffer is required, which will accidentally increase noise and DC error).

使用RDode表示等效二极管电阻，CTOT表示等效二极管电容加上OPA380输入电容，噪声零点fZ由以下公式计算：

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Figure 6: A cross -resistant circuit structure with variable total noise gain and integrated noise gain

These circuit structures The effect on the output noise is shown in Figure 8, and the effect on the integrated output noise is shown in Figure 9. 2 Polar Bartworth Filter (the largest flat in the band) is created by selecting the filter value by using the following formula:

Yes:

[

[ [

[

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The circuit in FIG. 6b attenuation at a speed of 20DB/Decade. The circuit with the additional filter shown in Figure 6C is attenuated at a speed of 40dB/Decade, thereby improving the noise performance.

FIG. 10 shows the effects of diode capacitors on integrated output noise, and use the circuit in Figure 6C.

For more information, please refer to the noise analysis of the FET transgender large -device noise analysis (SBOA060) and high -speed computing amplifier (SBOA066) downloaded from the TI website.

circuit board layout

The minimum optical diode capacitance and strange capacitance of the convergence (inverter input). This capacitor causes the voltage noise of the operation amplifier to be amplified (high frequency release). The use of low noise voltage sources reverse bias photoelectric diode can significantly reduce its capacitance. The smaller photoelectric diode has lower capacitors. Use optical devices to concentrate light on a small photoelectric diode.

Circuit board leakage will reduce the performance of other well -designed amplifiers. Clean the circuit board carefully. Surrounding and knots and the protection trajectory of the circuit board driven by the same voltage can help control the leakage, as shown in Figure 11.

Other methods to measure the small current

The number of amplifiers is used to compress the current input current to a narrower range. The wide input dynamic range is 8 years, or 100 palsa to 10 mA, which can accommodate 12 -bit ADC input. (Suggestions: LOG101, LOG102, LOG104, LOG112.)

A very small current can be accurately measured by integrating current on the capacitor. (Recommended products: IVC102)

Low -level current can be converted into high -resolution data words. (Recommended product: DDC112)

For more information about available products, please use the above -mentioned specific model names or use keyword transimpedance and searches for numbers.

Rongtability load and stability

OPA380 series operational amplifier can drive up to 500PF pure capacitor load. Increasing gain can enhance the capabilities of the amplifier driver to drive a larger capacitance load (see typical characteristic curves, small signal over pumping and capacitance load).

The improvement method is to insert a resistor of 10 insert a series in a series in a 10Ω load. This reduces the bell when the large capacitor load is loaded, while maintaining the accuracy of DC.

Drive the fast 16 -bit modulus converter (ADC)

OPA380 series is an ADS8411 optimized for driving fast 16 -bit. OPA380 computing amplifier buffer converter input capacitance and the charge injection generated by it, at the same time provides signal gain. Figure 12 shows the ADS8411 16 -bit of OPA380 in a single -end method interface, 2MSPS ADC. For more information, see the ADS8411 data table.