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參數(shù)資料
| 型號： | ZL40121DCA |
| 廠商： | Zarlink Semiconductor Inc. |
| 英文描述： | Low Power,Current Feedback Dual Operational Amplifier |
| 中文描述： | 低功耗，電流反饋雙路運算放大器 |
| 文件頁數(shù)： | 2/16頁 |
| 文件大小： | 288K |
| 代理商： | ZL40121DCA |
ZL40121
Data Sheet
2
Zarlink Semiconductor Inc.
Application Notes
Current Feedback Op Amps
Current feedback op amps offer several advantages over voltage feedback amplifiers:
The architecture of the current feedback opamp consists of a high impedance non-inverting input and a low
impedance inverting input which is always feedback connected. The error current is amplified by a transimpedance
amplifier which can be considered to have gain
AC bandwidth not dependent on closed loop gain
High Slew Rate
Fast settling time
where Z
o
is the DC gain.
It can be shown that the closed loop non-inverting gain is given by
where Av is the DC closed loop gain, R
f
is the feedback resistor. The closed loop bandwidth is therefore given by
GB
R
and for low values of closed loop gain Av depends only on the feedback resistor R
f
and not the closed loop gain.
This can readily be seen from the performance characteristic frequency response graph with varying R
f
It can be shown that increasing the value of R
f
Using a resistor value of R
f
=510
for Av=+2 V/V gives good stability and bandwidth. However since requirements
for stability and bandwidth vary it may be worth some experimentation to find the optimal R
f
for a given application.
Increases closed loop stability
Decreases loop gain
Decreases bandwidth
Reduces gain peaking
Reduces overshoot
Layout Considerations
Correct high frequency operation requires a considered PCB layout as stray capacitances have a strong influence
over high frequency operation for this device. This is particularly important for high performance current feedback
opamps. The Zarlink evaluation board serves as a good example layout that should be copied. The following
guidelines should be followed:
Include 6.8uF tantalum and 0.1uF ceramic capacitors on both positive and negative supplies
Remove the ground plane under and around the part, especially near the input and output pins to reduce
parasitic capacitances
Minimize all trace lengths to reduce series inductance
+
=
o
o
f
f
j
Z
f
Z
1
)
(
+
=
o
o
f
Z
f
fR
j
Av
Vin
Vout
1
f
OL
f
o
o
CL
R
Z
f
BW
=
=
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| ZL40122_06 | 制造商:ZARLINK 制造商全稱:Zarlink Semiconductor Inc 功能描述:High Speed, Current Feedback Quad Operational Amplifier |
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