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參數(shù)資料
| 型號： | OP179 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Rail-to-Rail High Output Current Operational Amplifiers |
| 中文描述： | 軌到軌高輸出電流運(yùn)算放大器 |
| 文件頁數(shù)： | 6/16頁 |
| 文件大?。?/td> | 228K |
| 代理商： | OP179 |
OP179/OP279
Typical Performance Graphs
–6–
REV. F
THEORY OF OPERATION
The OP179/OP279 is the latest entry in Analog Devices’ ex-
panding family of single-supply devices, designed for the multi-
media and telecom marketplaces. It is a high output current
drive, rail-to-rail input /output operational amplifier, powered
from a single +5 V supply. It is also intended for other low
supply voltage applications where low distortion and high out-
put current drive are needed. To combine the attributes of high
output current and low distortion in rail-to-rail input/output
operation, novel circuit design techniques are used.
For example, Figure 1 illustrates a simplified equivalent circuit
for the OP179/OP279’s input stage. It is comprised of two PNP
differential pairs, Q5-Q6 and Q7-Q8, operating in parallel, with
diode protection networks. Diode networks D5-D6 and D7-D8
serve to clamp the applied differential input voltage to the
OP179/OP279, thereby protecting the input transistors against
avalanche damage. The fundamental differences between these
two PNP gain stages are that the Q7-Q8 pair are normally OFF
and that their inputs are buffered from the operational amplifier
inputs by Q1-D1-D2 and Q9-D3-D4. Operation is best under-
stood as a function of the applied common-mode voltage:
When the inputs of the OP179/OP279 are biased midway be-
tween the supplies, the differential signal path gain is controlled
by the resistively loaded (via R7, R8) Q5-Q6. As the input
common-mode level is reduced toward the negative supply
(V
NEG
or GND), the input transistor current sources, I1 and I3,
are forced into saturation, thereby forcing the Q1-D1-D2 and
Q9-D3-D4 networks into cutoff; however, Q5-Q6 remain
active, providing input stage gain. On the other hand, when the
common-mode input voltage is increased toward the positive
supply, Q5-Q6 are driven into cutoff, Q3 is driven into satura-
tion, and Q4 becomes active, providing bias to the Q7-Q8 dif-
ferential pair. The point at which the Q7-Q8 differential pair
becomes active is approximately equal to (V
POS
– 1 V).
I2
R5
4k
V
D7
I1
R6
4k
V
D8
D5
D6
R3
2.5k
V
R4
2.5k
V
Q4
Q3
Q2
Q5
Q6
Q9
Q1
R1
6k
V
R2
3k
V
V
POS
V
NEG
R7
2.2k
V
R8
2.2k
V
I3
D1
D2
D3
D4
V
O
–
+
IN–
IN+
Q8
Q7
Figure 22. OP179/OP279 Equivalent Input Circuit
The key issue here is the behavior of the input bias currents in
this stage. The input bias currents of the OP179/OP279 over
the range of common-mode voltages from (V
NEG
+ 1 V) to
(V
POS
– 1 V) are the arithmetic sum of the base currents in Q1-
Q5 and Q9-Q6. Outside of this range, the input bias currents
are dominated by the base current sum of Q5-Q6 for input
signals close to V
NEG
, and of Q1-Q5 (Q9-Q6) for input signals
close to V
POS
. As a result of this design approach, the input bias
currents in the OP179/OP279 not only exhibit different ampli-
tudes, but also exhibit different polarities. This input bias cur-
rent behavior is best illustrated in Figure 3. It is, therefore, of
paramount importance that the effective source impedances
connected to the OP179/OP279’s inputs are balanced for opti-
mum dc and ac performance.
100
60
0
10
10k
1k
100
1
40
20
80
FREQUENCY – Hz
V
!
H
V
S
= +5V
T
A
= +25
8
C
Figure 19. Voltage Noise Density vs.
Frequency
120
60
0
1k
1M
100k
10k
100
40
20
80
100
FREQUENCY – Hz
C
T
A
= +25
8
C
V
S
6
2.5V
Figure 21. Common-Mode
Rejection vs. Frequency
COMMON-MODE VOLTAGE – Volts
60
0
5
30
10
1
20
0
50
40
4
3
2
V
!
H
V
S
= +5V
T
= +25
8
C
FREQUENCY = 1kHz
Figure 20. Voltage Noise Density vs.
Common-Mode Voltage
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| OP279GP | Rail-to-Rail High Output Current Operational Amplifiers |
| OP181GP | Ultralow Power, Rail-to-Rail Output Operational Amplifiers |
| OP181GS | Ultralow Power, Rail-to-Rail Output Operational Amplifiers |
| OP181 | Ultralow Power, Rail-to-Rail Output Operational Amplifiers |
| OP186 | 5 uA, Rail-to-Rail Output Operational Amplifier |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OP179_02 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Rail-to-Rail High Output Current Operational Amplifiers |
| OP179GRT | 制造商:Analog Devices 功能描述:OP-AMP, 5000 uV OFFSET-MAX, 5 MHz BAND WIDTH, PDSO5 |
| OP179GRT-REEL | 制造商:Analog Devices 功能描述:OP Amp Single GP R-R I/O 12V 5-Pin SOT-23 T/R 制造商:Rochester Electronics LLC 功能描述:RAIL-RAIL HIGH OUTPUT OPAMP - Tape and Reel |
| OP179GRT-REEL7 | 制造商:Analog Devices 功能描述:OP Amp Single GP R-R I/O 12V 5-Pin SOT-23 T/R |
| OP179GRTZ-REEL | 制造商:Analog Devices 功能描述:OP AMP SGL GP R-R I/O 12V 5PIN SOT-23 - Tape and Reel |
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