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參數(shù)資料
| 型號： | OP493 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Precision, Micropower Operational Amplifiers(精密的微功率四運(yùn)放) |
| 中文描述： | 精密，微功耗運(yùn)算放大器（精密的微功率四運(yùn)放） |
| 文件頁數(shù)： | 11/16頁 |
| 文件大?。?/td> | 273K |
| 代理商： | OP493 |
OP193/OP293/OP493
REV. A
–11–
6
5
7
4
1
2
3
V–
V+
OP193
100k
100k
Figure 27. High Resolution Offset Nulling Circuit
A Micropower False-Ground Generator
Some single supply circuits work best when inputs are biased
above ground, typically at 1/2 of the supply voltage. In these
cases a false ground can be created by using a voltage divider
buffered by an amplifier. One such circuit is shown in Figure 28.
T his circuit will generate a false-ground reference at 1/2 of the
supply voltage, while drawing only about 27
μ
A from a 5 V sup-
ply. T he circuit includes compensation to allow for a 1
μ
F by-
pass capacitor at the false-ground output. T he benefit of a large
capacitor is that not only does the false ground present a very
low dc resistance to the load, but its ac impedance is low as well.
T he OP193 can both sink and source more than 5 mA, which
improves recovery time from transients in the load current.
6
7
2
3
10k
OP193
100
4
+5V OR +12V
0.022μF
1μF
240k
240k
1μF
+2.5V OR +6V
Figure 28. A Micropower False-Ground Generator
A Battery Powered Voltage Reference
T he circuit of Figure 29 is a battery-powered voltage reference
that draws only 17
μ
A of supply current. At this level, two AA
alkaline cells can power this reference for more than 18 months.
At an output voltage of 1.23 V @ 25
°
C, drift of the reference is
only 5.5
μ
V/
°
C over the industrial temperature range. Load
regulation is 85
μ
V/mA with line regulation at 120
μ
V/V.
Design of the reference is based on the Brokaw bandgap core
technique. Scaling of resistors R1 and R2 produces unequal cur-
rents in Q1 and Q2. T he resulting
V
BE
across R3 creates a tem-
perature-proportional voltage (PT AT ) which, in turn, produces
a larger temperature-proportional voltage across R4 and R5, V1.
T he temperature coefficient of V1 cancels (first order) the
complementary to absolute temperature (CT AT ) coefficient of
V
BE1
. When adjusted to 1.23 V @ +25
°
C, output voltage
tempco is at a minimum. Bandgap references can have start-up
problems. With no current in R1 and R2, the OP193 is beyond
its positive input range limit and has an undefined output state.
Shorting Pin 5 (an offset adjust pin) to ground forces the output
high under these circumstances and insures reliable startup
without significantly degrading the OP193’s offset drift.
6
7
2
3
C1
1000pF
OP193
V
BE2
4
R2
1.5M
Q1
V
OUT
(1.23V @ 25
°
C)
5
R1
240k
V+
(+2.5V TO +36V)
Q2
1
2
3
7
6
5
V
BE1
MAT-01AH
V
BE
R3 68k
R5 20k
OUTPUT
ADJUST
R4
130k
V1
Figure 29. A Battery Powered Voltage Reference
A Single-Supply Current Monitor
Current monitoring essentially consists of amplifying the voltage
drop across a resistor placed in series with the current to be
measured. T he difficulty is that only small voltage drops can be
tolerated, and with low precision op amps this greatly limits the
overall resolution. T he single-supply current monitor of Figure
30 has a resolution of 10
μ
A and is capable of monitoring 30
mA of current. T his range can be adjusted by changing the cur-
rent sense resistor R1. When measuring total system current, it
may be necessary to include the supply current of the current
monitor, which bypasses the current sense resistor, in the final
result. T his current can be measured and calibrated (together
with the residual offset) by adjustment of the offset trim potenti-
ometer, R2. T his produces a deliberate temperature dependent
offset. However, the supply current of the OP193 is also propor-
tional to temperature, and the two effects tend to track. Current
in R4 and R5, which also bypasses R1, can be adjusted via a
gain trim.
6
7
2
3
OP193
4
R2
100k
V
OUT =
100mV/mA(I
TEST
)
5
V+
1
R2
9.9k
R3
100k
R5
100
R1
1
TO CIRCUIT
UNDER TEST
I
TEST
Figure 30. Single-Supply Current Monitor
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OP4930003SR | 制造商:Analog Devices 功能描述: |
| OP493EP | 制造商:Rochester Electronics LLC 功能描述:MICROPOWER RAIL/RAIL - Bulk |
| OP493ES | 制造商:AD 制造商全稱:Analog Devices 功能描述:Precision, Micropower Operational Amplifiers |
| OP493ES-REEL | 制造商:AD 制造商全稱:Analog Devices 功能描述:Precision, Micropower Operational Amplifiers |
| OP493FP | 制造商:Rochester Electronics LLC 功能描述:MICROPOWER RAIL/RAIL - Bulk 制造商:Analog Devices 功能描述: |
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