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AD8601ARTZ-REEL7 参数 Datasheet PDF下载

AD8601ARTZ-REEL7图片预览
型号: AD8601ARTZ-REEL7
PDF下载: 下载PDF文件 查看货源
内容描述: 精密CMOS单电源,轨到轨输入/输出宽带运算放大器 [Precision CMOS, Single-Supply, Rail-to-Rail, Input/Output Wideband Operational Amplifiers]
分类和应用: 运算放大器放大器电路光电二极管PC
文件页数/大小: 24 页 / 356 K
品牌: ADI [ ADI ]
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AD8601/AD8602/AD8604  
The current through the photodiode is proportional to the incident  
light power on its surface. The 4.7 MΩ resistor converts this current  
into a voltage, with the output of the AD8601 increasing at 4.7 V/μA.  
The feedback capacitor reduces excess noise at higher frequencies  
by limiting the bandwidth of the circuit to  
INPUT OVERVOLTAGE PROTECTION  
As with any semiconductor device, if a condition could exist  
that could cause the input voltage to exceed the power supply,  
the device’s input overvoltage characteristic must be considered.  
Excess input voltage energizes the internal PN junctions in the  
AD860x, allowing current to flow from the input to the supplies.  
1
BW =  
(1)  
2π  
(
4.7 Mꢀ CF  
)
This input current does not damage the amplifier, provided it is  
limited to 5 mA or less. This can be ensured by placing a resistor in  
series with the input. For example, if the input voltage could  
exceed the supply by 5 V, the series resistor should be at least  
(5 V/5 mA) = 1 kΩ. With the input voltage within the supply  
rails, a minimal amount of current is drawn into the inputs,  
which, in turn, causes a negligible voltage drop across the series  
resistor. Therefore, adding the series resistor does not adversely  
affect circuit performance.  
Using a 10 pF feedback capacitor limits the bandwidth to  
approximately 3.3 kHz.  
10pF  
(OPTIONAL)  
4.7MΩ  
V
D1  
OUT  
4.7V/µA  
AD8601  
OVERDRIVE RECOVERY  
Figure 56. Amplifier Photodiode Circuit  
Overdrive recovery is defined as the time it takes the output of  
an amplifier to come off the supply rail when recovering from  
an overload signal. This is tested by placing the amplifier in a  
closed-loop gain of 10 with an input square wave of 2 V p-p  
while the amplifier is powered from either 5 V or 3 V.  
HIGH SIDE AND LOW SIDE, PRECISION CURRENT  
MONITORING  
Because of its low input bias current and low offset voltage, the  
AD860x can be used for precision current monitoring. The true  
rail-to-rail input feature of the AD860x allows the amplifier to  
monitor current on either the high side or the low side. Using both  
amplifiers in an AD8602 provides a simple method for monitoring  
both current supply and return paths for load or fault detection.  
Figure 57 and Figure 58 demonstrate both circuits.  
3V  
The AD860x has excellent recovery time from overload conditions.  
The output recovers from the positive supply rail within 200 ns  
at all supply voltages. Recovery from the negative rail is within  
500 ns at a 5 V supply, decreasing to within 350 ns when the  
device is powered from 2.7 V.  
POWER-ON TIME  
R2  
The power-on time is important in portable applications where  
the supply voltage to the amplifier may be toggled to shut down  
the device to improve battery life. Fast power-up behavior ensures  
that the output of the amplifier quickly settles to its final voltage,  
improving the power-up speed of the entire system. When the  
supply voltage reaches a minimum of 2.5 V, the AD860x settles to  
a valid output within 1 μs. This turn-on response time is faster  
than many other precision amplifiers, which can take tens or  
hundreds of microseconds for their outputs to settle.  
249k  
MONITOR  
OUTPUT  
Q1  
2N3904  
3V  
R1  
100Ω  
1/2 AD8602  
RETURN TO  
GROUND  
R
SENSE  
0.1Ω  
Figure 57. Low-Side Current Monitor  
USING THE AD8602 IN HIGH SOURCE IMPEDANCE  
APPLICATIONS  
R
0.1  
SENSE  
I
L
V+  
3V  
The CMOS rail-to-rail input structure of the AD860x allows  
these amplifiers to have very low input bias currents, typically  
0.2 pA. This allows the AD860x to be used in any application  
that has a high source impedance or must use large value  
resistances around the amplifier. For example, the photodiode  
amplifier circuit shown in Figure 56 requires a low input bias  
current op amp to reduce output voltage error. The AD8601  
minimizes offset errors due to its low input bias current and low  
offset voltage.  
3V  
R1  
100Ω  
1/2 AD8602  
Q1  
2N3905  
MONITOR  
OUTPUT  
R2  
2.49kΩ  
Figure 58. High-Side Current Monitor  
Rev. G | Page 16 of 24