Features

suitable for+3V,+5V or ± 5V applications

large input co-mode range 0V lt; vcm lt; vs-1.2V [123 [123 ]

output swing to the ground saturation

-3db bandwidth 125MHz

± 0.1db bandwidth 30MHz

low power current 5mA (each amplifier)

conversion rate 275V/microsecond

low offset voltage maximum 4mv [123 [123 [123 ]

output current ± 100ma

High open ring gain 80db

Differential gain 0.05%

# 8226; difference 0.05 '

Application

Video amplifier

pcmcia application

a/ a/ D drive

line drive

Portable computer

High -speed communication

RGB printer , Fax machine, scanner

Broadcasting equipment

Active filtering

Order information

General description

EL2250C

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EL2450C is part of the fastest single -power computing amplifier series in the electronics industry. The previous single power supply amplifier is usually limited to the bandwidth and conversion rate of EL2250C/EL2450C. 125MHz bandwidth, 275V/microsecond conversion rate, and 0.05%/0.05 ° Differential gain/differential phase make this part is very suitable for single power or dual power video speed applications. Due to its voltage feedback structure, the amplifier can accept non -contribution feedback network and allow them to simulate filtering applications. These inputs can sensorize a signal of 1.2V under the power rail and the top power rail under the bottom of the bottom. The load resistance is connected and the output is completely swinged to the ground without saturation. The output can also drive to the top rail within 1.2V. EL2250C/EL2450C will output ± 100mA and work under a single power supply voltage as low as 2.7V to make it an ideal choice for portable low -power applications. EL2250C/EL2450C can be used in PDIP, so the packaging uses industry standard pins. Both components work within the industrial temperature range of -40 ° C to+85 ° C. It is part of the single-power operation amplifier series. For single -placing large -device applications, see EL2150C/EL2157C. For dual amplifiers and three amplifiers with a lower power and output voltage clip, see EL2257C/EL2357C.

Connection Figure

Typical performance curve

Application information

Product description [ 123]

EL2250C/EL2450C is part of the fastest single -power operation amplifier series in the industry. Connecting the voltage follow-up mode, their -3DB bandwidth is 125MHz, while maintaining a conversion rate of 275V/microsecond. Because the range of input and output includes grounding, these amplifiers are optimized for single power operations, but they will also accept dual power. They work within the total power supply voltage range of+2.7V or high+12V, so they are very suitable for+3V applications, especially portable computers.

Although many amplifiers claim to work on a single power supply, some amplifiers can detect ground on its input terminal, most amplifiers cannot truly output the ground. If they successfully drive to the ground, the amplifier is usually saturated, causing distortion and recovery delay. However, EL2250C/EL2450C has built -in special circuits to allow the output to follow the input signal ground without recovery delay.

Power bypass and printing circuits

Circuit plate layout

Like any high -frequency device, good printing circuit board layout is a necessary condition for the best performance. It is strongly recommended to carry out ground flooring. The length of the lead should be as short as possible. It must be completely bypassed the power of the power to reduce the risk of oscillation. The combination of 4.7 μF 器 capacitor and 0.1 μF ceramic capacitor works well when placed at each power supply. For single power operations, when the ground pins are connected to the ground plane, a 4.7μF 钽 capacitor and a 0.1 μF ceramic capacitor are parallel to VS+and ground pins.

In order to obtain good communication performance, parasitic capacitors should be maintained at the minimum value. The ground plane structure should be adopted. Carbon or metal membrane resistors are acceptable. Due to its additional series inductance, the metal membrane resistor makes the peak and bandwidth slightly smaller. If possible, avoid using sockets, especially SO packs. The socket increases parasitic inductance and capacitance, which will cause some additional peaks and overruns.

Power supply voltage range and single power supply

Operation

The design working voltage span of the design of the design of EL2250C/EL2450C is greater than 2.7V, less than 12V. In fact, this means that EL2250C/EL2450C will work on dual power supply from ± 1.35V to ± 6V. EL2250C/EL2450C will work on a single power supply of+2.7V to+12V. Performance has been optimized for a single+5V power supply.

Inserting 8 and 4 are the power plugs on EL2250C. The positive power supply is connected to the foot 8. When used in a single power supply mode, the needle 4 grounds. When used in dual power mode, the negative power supply is connected to the pin 4.

Inserting 4 and 11 are the power plugs on EL2450C. The positive power supply is connected to the foot 4. When used in a single power supply mode, the needle is 11 ground. When used in dual power mode, the negative power supply is connected to the pin 11.

With the continuous decrease of the power supply voltage, it is necessary to provide the input and output voltage range that closer to the power supply voltage as close as possible. The input voltage range of EL2250C/EL2450C includes the negative electrode power supply and extends to the 1.2V range of the positive power supply. Therefore, for example, on a single+5V power supply, the input range of EL2250C/EL2450C is from 0V to 3.8V.

The output range of EL2250C/EL2450C is also quite large. It includes negative and extends to the top 1V with a 1kΩ load. Therefore, on the+5V power supply, the output can swing from 0V to+4V. On the split power supply, the output will swing ± 4V. If the load resistance is connected to the negative, and the split power supply is used, the output range will be extended to a negative.

Selection of the feedback resistance

The feedback resistance and input capacitance formation. When the magnetic pole becomes larger, the phase margin decreases. This increases the peak of the time domain and the peak of the frequency domain. Therefore, in order to achieve the best performance, RF should not exceed the maximum value. If a larger RF value must be used, the small electric container in the slightly slightly Fatra range with RF can help reduce this bell and peak, but the cost is to reduce the bandwidth.

As far as the output level of the amplifier is concerned, RF+RG appears parallel with RL to obtain gains other than +1. When this combination changes, the bandwidth will decrease. Therefore, RF has a minimum value that should not exceed to obtain the best performance.

For AV +1, RF 0Ω is the best value. For AV -1 or +2 (noise gain is 2), the best response is obtained when RF is between 500Ω and 1kΩ. For AV -4 or +5 (noise gain is 5), keep RF between 2kΩ and 10kΩ.

Video performance

In order to obtain good video performance, the amplifier needs to maintain the same outputImpedance and the same frequency response, because the DC level changes at the output end. This may be difficult when the standard video load of 150Ω is driven, because the output current changes with the DC level. The differential gain and differential phase of the EL2250C/EL2450C are specified when the black level of the output video signal is set to+1.2V. In this way, even if the gain is +2 configuration, it can provide sufficient space for synchronization pulses. This causes the DG and DP specifications to be 0.05%and 0.05 °, respectively, while driving 150Ω at the same time with +2 gain. Set the black level to other values (although acceptable) will affect peak performance. For example, check the single power supply DG and DP curves of RL 150Ω. If the output black level clamping from 1.2V to 0.6V Dg/DP, then 0.05%/0.05 ° to 0.08%/0.25 ° pay attention, at +2 gain at +2 gain In the configuration, this is the lowest black level, so that the synchronization prompts will not be lower than 0V.

If the application requires output grounding, the output stage of EL2250C/EL2450C is the same as that of all other single power supply, and a external drop -down resistor connected to the ground is required. As mentioned above, the current flowing through the resistor becomes the DC bias current of the output stage NPN transistor. In this way, the current is close to zero, the NPN is closed, and DG and DP will increase. As the load resistance value increases, this becomes more critical. When the driver is light load (such as 1kΩ), if the black level is kept above 1.25V, the DG and DPs are 0.03%and 0.03 °, respectively.

For other bias conditions, see the relationship curve of differential gains and differential phases and input voltage.

Output driving capacity

Although the power supply current of EL2250C/EL2450C is 5 mAh, it can provide ± 100 mA -out output current under 10Ω load, or provide ± under 50Ω load. 60 mAh output current. With this large output current capability, the 50Ω load can drive to ± 3V and VS ± 5V, making it an excellent choice, driving a driver isolation transformer at telecommunications.

Drive cable and capacitor load

When used as a cable drive, it is recommended to use two -terminal connection to achieve non -reflection performance. For these applications, the rear string resistance will disconnect EL2250C/EL2450C from the cable, and allows a wide range of capacitors to drive. However, other applications may have high -capacitance loads and no rear resistance. In these applications, small series connected resistors (usually between 5Ω and 50Ω) can be connected in series with the output to eliminate most peak values. Then, you can choose the gain resistor (RG) to compensate for any gain loss of the additional resistor at the output end.

Video synchronization pulse elimination application

When the input voltage is negative, all CMOS modulus converters (A/DS) existquestion. Because synchronous prompts do not contain useful video information, and it is a negative pulse, we can cut it off.

FIG. 1 shows the unit gain connection amplifier A of EL2250C. Figure 2 shows a complete input video signal applied to the input terminal, and the output signal that removes negative synchronization pulses.

Short -circuit current limit

EL2250C/EL2450C has an internal short -circuit protection circuit, which protects it when the output is short -circuit in the power rail. This limit is set to about 100mA nominal, and decreases as the knot temperature rises. It is used to deal with temporary short circuits. If the output is short -term, the power consumption is easy to increase, which will damage the part. If the output current has never exceeded ± 90mA, it remains to the maximum reliability. When the output is short -term, the radiator may be required to keep the knot temperature below the absolute maximum value.

Power consumption

Under the high output driving capacity of EL2250C/EL2450C, under a certain load current, it may exceed the absolute maximum knot temperature of more than 150 ° C. Therefore, calculating the maximum knot temperature for determining the power supply voltage and load to keep the EL2250C/EL2450C in the safe operating area, and the conditions or packaging types need to be modified.

The maximum power consumption allowed in the package is determined based on [1]:

In style: tjmax the highest knot temperature; tamax the highest ambient temperature; qja; Thermal resistance of packaging; pdmax maximum power consumption in packaging.

集成电路实际产生的最大功耗是总静态电源电流乘以总电源电压，再加上集成电路中由于负载而产生的功率，或[2]

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In the formula: N the number of amplifiers; vs total power voltage; ISMAX maximum power supply current of each amplifier; maximum output voltage of vout application; RL grounding load resistance.

If we will equal two PDMAX equations [1] and [2], and solve VS, we can get the curve clan of various loads and output voltages according to [3]:

[[

123]

The following Figure 3 to Figure 6 shows the comparison of the total single power supply voltage of various output voltage fluctuations of PDIP and SO packages with RL. The temperature of the curve assumes the worst case is TA +85 ° C, and the temperature of each amplifier is 6.5mA.

EL2250C/EL2450C宏模型（一个放大器）

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