Datasheet > 放大器电路 > 运算放大器> ADA4857-1YRZ-R7

ADA4857-1YRZ-R7

更新时间： 2024-02-05 17:00:44

品牌	Logo	应用领域
亚德诺 - ADI		运算放大器放大器电路光电二极管
页数	文件大小	规格书
20页	588K
描述
Ultralow Distortion, Low Power, Low Noise, High Speed Op Amp

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ADA4857-1YRZ-R7 技术参数

是否无铅：	不含铅	是否Rohs认证：	符合
生命周期：	Active	零件包装代码：	SOIC
包装说明：	SOP,	针数：	8
Reach Compliance Code：	unknown	风险等级：	5.35
Is Samacsys：	N	放大器类型：	OPERATIONAL AMPLIFIER
最大平均偏置电流 (IIB)：	3.3 µA	标称共模抑制比：	86 dB
最大输入失调电压：	4.5 µV	JESD-30 代码：	R-PDSO-G8
JESD-609代码：	e3	长度：	4.9 mm
湿度敏感等级：	1	负供电电压上限：	-5.5 V
标称负供电电压 (Vsup)：	-5 V	功能数量：	1
端子数量：	8	最高工作温度：	125 °C
最低工作温度：	-40 °C	封装主体材料：	PLASTIC/EPOXY
封装代码：	SOP	封装形状：	RECTANGULAR
封装形式：	SMALL OUTLINE	峰值回流温度（摄氏度）：	260
座面最大高度：	1.75 mm	标称压摆率：	2800 V/us
子类别：	Operational Amplifier	供电电压上限：	5.5 V
标称供电电压 (Vsup)：	5 V	表面贴装：	YES
温度等级：	AUTOMOTIVE	端子面层：	MATTE TIN
端子形式：	GULL WING	端子节距：	1.27 mm
端子位置：	DUAL	处于峰值回流温度下的最长时间：	40
宽度：	3.9 mm	Base Number Matches：	1

ADA4857-1YRZ-R7 数据手册

ADA4857-1/ADA4857-2

NOISE

CIRCUIT CONSIDERATIONS

To analyze the noise performance of an amplifier circuit,

identify the noise sources and then determine if the source has a

significant contribution to the overall noise performance of the

amplifier. To simplify the noise calculations, noise spectral densities

were used rather than actual voltages to leave bandwidth out of the

expressions (noise spectral density, which is generally expressed

in nV/√Hz, is equivalent to the noise in a 1 Hz bandwidth).

Careful and deliberate attention to detail when laying out the

ADA4857 board yields optimal performance. Power supply

bypassing, parasitic capacitance, and component selection all

contribute to the overall performance of the amplifier.

PCB LAYOUT

Because the ADA4857 can operate up to 850 MHz, it is essential

that RF board layout techniques be employed. All ground and

power planes under the pins of the ADA4857 should be cleared

of copper to prevent the formation of parasitic capacitance between

the input pins to ground and the output pins to ground. A single

mounting pad on the SOIC footprint can add as much as 0.2 pF

of capacitance to ground if the ground plane is not cleared from

under the mounting pads. The low distortion pinout of the

ADA4857 increases the separation distance between the inputs

and the supply pins, which improves the second harmonics. In

addition, the feedback pin reduces the distance between the

output and the inverting input of the amplifier, which helps

minimize the parasitic inductance and capacitance of the

feedback path, reducing ringing and peaking.

The noise model shown in Figure 47 has six individual noise

sources: the Johnson noise of the three resistors, the op amp

voltage noise, and the current noise in each input of the amplifier.

Each noise source has its own contribution to the noise at the

output. Noise is generally referred to input (RTI), but it is often

simpler to calculate the noise referred to the output (RTO) and

then divide by the noise gain to obtain the RTI noise.

N, R2

GAIN FROM

A TO OUTPUT

4kTR2

NOISE GAIN =

N, R1

N–

NG = 1 +

4kTR1

OUT

N, R3

POWER SUPPLY BYPASSING

N+

GAIN FROM

B TO OUTPUT

= –

Power supply bypassing for the ADA4857 was optimized for

frequency response and distortion performance. Figure 42

shows the recommended values and location of the bypass

capacitors. The 0.1 μF bypassing capacitors should be placed as

close as possible to the supply pins. Power supply bypassing is

critical for stability, frequency response, distortion, and PSR

performance. The capacitor between the two supplies helps

improve PSR and distortion performance. The 10 μF electrolytic

capacitors should be close to the 0.1 μF capacitors but it is not as

critical. In some cases, additional paralleled capacitors can help

improve frequency and transient response.

4kTR3

R1 + R2

+ 4kTR3 + 4kTR1

R1 × R2

R1 + R2

RTI NOISE =

R3 + I

+ 4kTR2

N+

N–

R1 + R2

RTO NOISE = NG × RTI NOISE

Figure 47. Op Amp Noise Analysis Model

All resistors have a Johnson noise that is calculated by

(4kBTR) .

where:

GROUNDING

k is Boltzmann’s Constant (1.38 × 10^–23J/K).

B is the bandwidth in Hertz.

T is the absolute temperature in Kelvin.

R is the resistance in ohms.

Ground and power planes should be used where possible. Ground

and power planes reduce the resistance and inductance of the

power planes and ground returns. The returns for the input,

output terminations, bypass capacitors, and R_Gshould all be

kept as close to the ADA4857 as possible. The output load

ground and the bypass capacitor grounds should be returned

to the same point on the ground plane to minimize parasitic

trace inductance, ringing, overshoot and to improve distortion

performance. The ADA4857 LFSCP packages feature an exposed

paddle. For optimum electrical and thermal performance,

solder this paddle to ground. For more information on high

speed circuit design, see A Practical Guide to High-Speed

Printed-Circuit-Board Layout at www.analog.com.

A simple relationship that is easy to remember is that a 50 Ω

resistor generates a Johnson noise of 1 nV/√Hz at 25°C.

In applications where noise sensitivity is critical, care must

be taken not to introduce other significant noise sources to

the amplifier. Each resistor is a noise source. Attention to the

following areas is critical to maintain low noise performance:

design, layout, and component selection. A summary of noise

performance for the amplifier and associated resistors can be

seen in Table 9.

Rev. 0 | Page 17 of 20

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ADA4857-1YRZ-R7 替代型号

型号	品牌	替代类型	描述	数据表
ADA4857-1YRZ	ADI	类似代替	Ultralow Distortion, Low Power, Low Noise, High Speed Op Amp

与ADA4857-1YRZ-R7相关器件

型号	品牌	获取价格	描述	数据表
ADA4857-1YRZ-RL	ADI	获取价格	Ultralow Distortion, Low Power, Low Noise, High Speed Op Amp
ADA4857-2	ADI	获取价格	Ultralow Distortion, Low Power, Low Noise, High Speed Op Amp
ADA4857-2YCP-EBZ	ADI	获取价格	Ultralow Distortion, Low Power, Low Noise, High Speed Op Amp
ADA4857-2YCPZ-R2	ADI	获取价格	Ultralow Distortion, Low Power, Low Noise, High Speed Op Amp
ADA4857-2YCPZ-R7	ADI	获取价格	Ultralow Distortion, Low Power, Low Noise, High Speed Op Amp
ADA4857-2YCPZ-RL	ADI	获取价格	Ultralow Distortion, Low Power, Low Noise, High Speed Op Amp
ADA4858-3	ADI	获取价格	Single-Supply, High Speed, Triple Op Amp with Charge Pump
ADA4858-3_16	ADI	获取价格	Single-Supply, High Speed, Triple Op Amp with Charge Pump
ADA4858-3ACP-EBZ	ADI	获取价格	Single-Supply, High Speed, Triple Op Amp with Charge Pump
ADA4858-3ACPZ-R2	ADI	获取价格	Single-Supply, High Speed, Triple Op Amp with Charge Pump

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