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參數資料
| 型號： | AD8531 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Low Cost, 250 mA Output Single-Supply Amplifiers(低成本,250mA輸出,單電源放大器) |
| 中文描述： | 低成本，250 mA輸出單電源放大器（低成本，250mA的輸出，單電源放大器） |
| 文件頁數： | 8/16頁 |
| 文件大小： | 220K |
| 代理商： | AD8531 |
AD8531/AD8532/AD8534
REV. A
–8–
APPLIC AT IONS
T HE ORY OF OPE RAT ION
T he AD8531/AD8532/AD8534 is an all-CMOS, high output
current drive, rail-to-rail input/output operational amplifier.
T his is the latest entry in Analog Devices’ expanding family of
single-supply devices for the multimedia and telecom market-
places. Its high output current drive and stability with heavy ca-
pacitive loads makes the AD8531/AD8532/AD8534 an excellent
choice as a drive amplifier for LCD panels.
Figure 32 illustrates a simplified equivalent circuit for the AD8531/
AD8532/AD8534. Like many rail-to-rail input amplifier configura-
tions, it is comprised of two differential pairs, one n-channel
(M1–M2) and one p-channel (M3–M4). T hese differential pairs
are biased by 50
μ
A current sources, each with a compliance
limit of approximately 0.5 V from either supply voltage rail. T he
differential input voltage is then converted into a pair of differen-
tial output currents. T hese differential output currents are then
combined in a compound folded-cascade second gain stage
(M5–M9). T he outputs of the second gain stage at M8 and M9
provide the gate voltage drive to the rail-to-rail output stage. Ad-
ditional signal current recombination for the output stage is
achieved through the use of transistors M11–M14.
In order to achieve rail-to-rail output swings, the AD8531/AD8532/
AD8534 design employs a complementary common-source output
stage (M15–M16). However, the output voltage swing is directly
dependent on the load current, as the difference between the out-
put voltage and the supply is determined by the AD8531/AD8532/
AD8534’s output transistors on-channel resistance (see Figures 8
and 9). T he output stage also exhibits voltage gain by virtue of
the use of common-source amplifiers; as a result, the voltage
gain of the output stage (thus, the open-loop gain of the device)
exhibits a strong dependence to the total load resistance at the
output of the AD8531/AD8532/AD8534.
50
μ
A
100
μ
A
100
μ
A
20
μ
A
V
B2
M2
M5
M8
M12
M15
M16
M11
OUT
M3
M4
M1
IN–
IN+
V
B3
M6
M7
M10
20
μ
A
M13
50
μ
A
V+
V–
M9
M14
Figure 32. AD8531/AD8532/AD8534 Simplified Equivalent
Circuit
Short-Circuit Protection
As a result of the design of the output stage for maximum load
current capability, the AD8531/AD8532/AD8534 does not have
any internal short-circuit protection circuitry. Direct connection of
the AD8531/AD8532/AD8534’s output to the positive supply
in single-supply applications will destroy the device. In those
applications where some protection is needed, but not at the ex-
pense of reduced output voltage headroom, a low value resistor
in series with the output, as shown in Figure 33, can be used.
T he resistor, connected within the feedback loop of the ampli-
fier, will have very little effect on the performance of the ampli-
fier other than limiting the maximum available output voltage
swing. For single +5 V supply applications, resistors less than
20
are not recommended.
+5V
R
X
20
V
OUT
V
IN
AD8532
Figure 33. Output Short-Circuit Protection
10
0%
500ns
500mV
100
90
V
S
=
6
1.35V
A
V
= 1
R
L
= 2k
T
A
= +25
8
C
Figure 30. Large Signal Transient
Response
10
0%
500ns
500mV
100
90
V
S
=
6
2.5V
A
V
= 1
R
L
= 2k
T
A
= +25
8
C
Figure 29. Large Signal Tran-
sient Response
10
0%
10
m
s
1V
100
90
1V
Figure 31. No Phase Reversal
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|---|---|
| AD8531_08 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Low Cost, 250 mA Output, Single-Supply Amplifiers |
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| AD8531AKS-REEL7 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Analog Devices 功能描述: |
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