LOG112 [BB]
Precision, High-Speed Transimpedance Amplifier; 精密，高速互阻抗放大器
| 型号： | LOG112 |
| 厂家： | 
BURR-BROWN CORPORATION |
| 描述： | Precision, High-Speed Transimpedance Amplifier |
| 文件： | 总18页 (文件大小：360K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
OPA380
OPA2380
SBOS291E − NOVEMBER 2003 − REVISED NOVEMBER 2004
Precision, High-Speed
Transimpedance Amplifier
FD EATURES
DESCRIPTION
> 1MHz TRANSIMPEDANCE BANDWIDTH
The OPA380 family of transimpedance amplifiers provides
high-speed (90MHz Gain Bandwidth [GBW]) operation, with
extremely high precision, excellent long-term stability, and
very low 1/f noise. It is ideally suited for high-speed
photodiode applications. The OPA380 features an offset
voltage of 25µV, offset drift of 0.1µV/°C, and bias current of
50pA. The OPA380 far exceeds the offset, drift, and noise
performance that conventional JFET op amps provide.
D
D
D
D
D
D
D
D
D
D
EXCELLENT LONG-TERM V
STABILITY
OS
BIAS CURRENT: 50pA (max)
OFFSET VOLTAGE: 25µV (max)
INPUT CURRENT RANGE: 10nA to 1mA
DRIFT: 0.1µV/°C (max)
GAIN BANDWIDTH: 90MHz
QUIESCENT CURRENT: 6.5mA
SUPPLY RANGE: 2.7V to 5.5V
SINGLE AND DUAL VERSIONS
MicroSize PACKAGE: MSOP-8
The signal bandwidth of a transimpedance amplifier depends
largely on the GBW of the amplifier and the parasitic
capacitance of the photodiode, as well as the feedback
resistor. The 90MHz GBW of the OPA380 enables a trans-
impedance bandwidth of > 1MHz in most configurations. The
OPA380 is ideally suited for fast control loops for power level
on an optical fiber.
AD PPLICATIONS
PHOTODIODE MONITORING
As a result of the high precision and low-noise characteristics
of the OPA380, a dynamic range of 5 decades can be
achieved. This capability allows the measurement of signal
currents in the order of 10nA, and up to 1mA in a single I/V
conversion stage. In contrast to logarithmic amplifiers, the
OPA380 provides very wide bandwidth throughout the full
dynamic range. By using an external pulldown resistor to
–5V, the output voltage range can be extended to include 0V.
D
D
D
PRECISION I/V CONVERSION
OPTICAL AMPLIFIERS
CAT-SCANNER FRONT-END
RF
+5V
7
The OPA380 (single) is available in MSOP-8 and SO-8
packages. The OPA2380 (dual) is available in the
miniature MSOP-8 package. They are specified from
–40°C to +125°C.
OPA380
2
VOUT
(0V to 4.4V)
6
RP
OPA380 RELATED DEVICES
Photodiode
(Optional
Pulldown
Resistor)
PRODUCT
OPA300
OPA350
OPA335
OPA132
OPA656/7
LOG112
LOG114
IVC102
FEATURES
67pF
1MΩ
150MHz CMOS, 2.7V to 5.5V Supply
−5V
500µV V , 38MHz, 2.5V to 5V Supply
OS
100kΩ
10µV V , Zero-Drift, 2.5V to 5V Supply
OS
3
16MHz GBW, Precision FET Op Amp, 15V
230MHz, Precision FET, 5V
75pF
LOG amp, 7.5 decades, 4.5V to 18V Supply
LOG amp, 7.5 decades, 2.25V to 5.5V Supply
Precision Switched Integrator
4
DDC112
Dual Current Input, 20-Bit ADC
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments
semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
ꢀꢁ ꢂ ꢃꢄ ꢅ ꢆꢇ ꢂꢈ ꢃ ꢉꢆꢉ ꢊꢋ ꢌꢍ ꢎ ꢏꢐ ꢑꢊꢍꢋ ꢊꢒ ꢓꢔ ꢎ ꢎ ꢕꢋꢑ ꢐꢒ ꢍꢌ ꢖꢔꢗ ꢘꢊꢓ ꢐꢑꢊ ꢍꢋ ꢙꢐ ꢑꢕꢚ ꢀꢎ ꢍꢙꢔ ꢓꢑꢒ
ꢓ ꢍꢋ ꢌꢍꢎ ꢏ ꢑꢍ ꢒ ꢖꢕ ꢓ ꢊ ꢌꢊ ꢓ ꢐ ꢑꢊ ꢍꢋꢒ ꢖ ꢕꢎ ꢑꢛꢕ ꢑꢕ ꢎ ꢏꢒ ꢍꢌ ꢆꢕꢜ ꢐꢒ ꢇꢋꢒ ꢑꢎ ꢔꢏ ꢕꢋꢑ ꢒ ꢒꢑ ꢐꢋꢙ ꢐꢎ ꢙ ꢝ ꢐꢎ ꢎ ꢐ ꢋꢑꢞꢚ
ꢀꢎ ꢍ ꢙꢔꢓ ꢑ ꢊꢍ ꢋ ꢖꢎ ꢍ ꢓ ꢕ ꢒ ꢒ ꢊꢋ ꢟ ꢙꢍ ꢕ ꢒ ꢋꢍꢑ ꢋꢕ ꢓꢕ ꢒꢒ ꢐꢎ ꢊꢘ ꢞ ꢊꢋꢓ ꢘꢔꢙ ꢕ ꢑꢕ ꢒꢑꢊ ꢋꢟ ꢍꢌ ꢐꢘ ꢘ ꢖꢐ ꢎ ꢐꢏ ꢕꢑꢕ ꢎ ꢒꢚ
Copyright 2003-2004, Texas Instruments Incorporated
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SBOS291E − NOVEMBER 2003 − REVISED NOVEMBER 2004
(1)
ELECTROSTATIC DISCHARGE SENSITIVITY
ABSOLUTE MAXIMUM RATINGS
Voltage Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7V
This integrated circuit can be damaged by ESD. Texas
Instruments recommends that all integrated circuits be
handledwith appropriate precautions. Failure to observe
(2)
Signal Input Terminals , Voltage . . . . . . . . . . −0.5V to (V+) + 0.5V
Current . . . . . . . . . . . . . . . . . . . . . 10mA
. . . . . . . . . . . . . . . . . . . . . . . . Continuous
(3)
Short-Circuit Current
proper handling and installation procedures can cause damage.
Operating Temperature Range . . . . . . . . . . . . . . . −40°C to +125°C
Storage Temperature Range . . . . . . . . . . . . . . . . . −65°C to +150°C
Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +150°C
Lead Temperature (soldering, 10s) . . . . . . . . . . . . . . . . . . . . . +300°C
ESD Rating (Human Body Model) . . . . . . . . . . . . . . . . . . . . . . . 2000V
ESD damage can range from subtle performance degradation to
complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could
cause the device not to meet its published specifications.
(1)
Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods
may degrade device reliability. These are stress ratings only, and
functional operation of the device at these or any other conditions
beyond those specified is not implied.
(1)
PACKAGE/ORDERING INFORMATION
PACKAGE
MARKING
PRODUCT
PACKAGE-LEAD
(2)
(3)
Input terminals are diode clamped to the power-supply rails. Input
signals that can swing more than 0.5V beyond the supply rails
should be current limited to 10mA or less.
OPA380
OPA380
OPA2380
MSOP-8
SO-8
AUN
OPA380A
BBX
Short-circuit to ground; one amplifier per package.
MSOP-8
(1)
For the most current package and ordering information, see the
Package Option Addendum located at the end of this data sheet.
PIN ASSIGNMENTS
Top View
OPA380
OPA2380
NC(1)
V+
NC(1)
1
2
3
4
8
7
6
5
Out A
1
2
3
4
8
7
6
5
V+
−
In
+In
−
In A
+In A
Out B
Out
−
In B
+In B
−
NC(1)
V
−
V
MSOP−8, SO−8
MSOP−8
NOTES: (1) NC indicates no internal connection.
2
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SBOS291E − NOVEMBER 2003 − REVISED NOVEMBER 2004
ELECTRICAL CHARACTERISTICS: OPA380 (SINGLE), V = 2.7V to 5.5V
S
Boldface limits apply over the temperature range, T = −40°C to +125°C.
A
All specifications at T = +25°C, R = 2kΩ connected to V /2, and V
= V /2, unless otherwise noted.
A
L
S
OUT
S
OPA380
TYP
MIN
MAX
PARAMETER
CONDITION
UNITS
OFFSET VOLTAGE
Input Offset Voltage
Drift
V
V
= +5V, V
= 0V
4
25
0.1
10
10
µV
OS
S CM
dV /dT
0.03
2.4
µV/°C
µV/V
µV/V
OS
vs Power Supply
Over Temperature
Long-Term Stability
PSRR
V
= +2.7V to +5.5V, V
= 0V
S
CM
V
= +2.7V to +5.5V, V
= 0V
S
CM
(1)
See Note (1)
1
Channel Separation, dc
µV/V
INPUT BIAS CURRENT
Input Bias Current
I
V
V
= V /2
3
50
pA
pA
B
CM
S
Over Temperature
Input Offset Current
Typical Characteristics
6
I
= V /2
100
OS
CM
S
NOISE
Input Voltage Noise, f = 0.1Hz to 10Hz
Input Voltage Noise Density, f = 10kHz
Input Voltage Noise Density, f > 1MHz
Input Current Noise Density, f = 10kHz
e
n
V
V
V
V
= +5V, V
= +5V, V
= +5V, V
= +5V, V
= 0V
= 0V
= 0V
= 0V
3
µV
PP
S
S
S
S
CM
CM
CM
CM
e
e
i
67
5.8
10
nV/√Hz
nV/√Hz
fA/√Hz
n
n
n
INPUT VOLTAGE RANGE
Common-Mode Voltage Range
Common-Mode Rejection Ratio
V
V−
(V+) − 1.8V
V
CM
CMRR
(V−) < V
CM
< (V+) – 1.8V
100
110
dB
INPUT IMPEDANCE
Differential Capacitance
Common-Mode Resistance and Inverting Input
Capacitance
1.1
pF
13
10 || 3
Ω || pF
OPEN-LOOP GAIN
Open-Loop Voltage Gain
A
0.1V < V < (V+) − 0.7V, V = 5V, V
= V /2
110
130
dB
OL
O
S
CM
S
0.1V < V < (V+) − 0.6V, V = 5V, V
= V /2,
O
S
CM
S
110
130
dB
T
= -40°C to +85°C
A
0V < V < (V+) − 0.7V, V = 5V, V
= 0V,
O
S
CM
106
120
dB
(2)
R
= 2kΩ to −5V
P
0V < V < (V+) − 0.6V, V = 5V, V
= 0V,
O
S
CM
106
120
dB
(2)
R
= 2kΩ to −5V , T = -40°C to +85°C
A
P
FREQUENCY RESPONSE
Gain-Bandwidth Product
Slew Rate
C = 50pF
L
GBW
SR
90
80
2
MHz
V/µs
µs
G = +1
V = +5V, 4V Step, G = +1
S
(3)
Settling Time, 0.01%
t
S
(4)(5)
Overload Recovery Time
V
• G = > V
100
ns
IN
S
OUTPUT
Voltage Output Swing from Positive Rail
Voltage Output Swing from Negative Rail
Voltage Output Swing from Positive Rail
Voltage Output Swing from Negative Rail
Output Current
R
= 2kΩ
= 2kΩ
400
60
600
100
600
0
mV
mV
mV
mV
L
L
R
(2)
(2)
R
R
= 2kΩ to −5V
= 2kΩ to −5V
400
−20
P
P
I
See Typical Characteristics
OUT
Short-Circuit Current
I
150
mA
SC
Capacitive Load Drive
C
See Typical Characteristics
40
LOAD
Open-Loop Output Impedance
R
f = 1MHz, I = 0A
Ω
O
O
POWER SUPPLY
Specified Voltage Range
Quiescent Current
Over Temperature
V
2.7
5.5
V
S
I
I
= 0A
6.5
8.3
mA
mA
Q
O
8.8
TEMPERATURE RANGE
Specified and Operating Range
Storage Range
−40
−65
+125
+150
°C
°C
Thermal Resistance
MSOP-8, SO-8
q
JA
150
°C/W
(1)
(2)
300-hour life test at 150°C demonstrated randomly distributed variation approximately equal to measurement repeatability of 1µV.
Tested with output connected only to R , a pulldown resistor connected between V
and −5V, as shown in Figure 5. See also applications section, Achieving
P
OUT
Output Swing to Ground.
(3)
(4)
(5)
Transimpedance frequency of 1MHz.
Time required to return to linear operation.
From positive rail.
3
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SBOS291E − NOVEMBER 2003 − REVISED NOVEMBER 2004
ELECTRICAL CHARACTERISTICS: OPA2380 (DUAL), V = 2.7V to 5.5V
S
Boldface limits apply over the temperature range, T = −40°C to +125°C.
A
All specifications at T = +25°C, R = 2kΩ connected to V /2, and V
= V /2, unless otherwise noted.
A
L
S
OUT
S
OPA2380
TYP
MIN
MAX
PARAMETER
CONDITION
UNITS
OFFSET VOLTAGE
Input Offset Voltage
Drift
V
V
= +5V, V
= 0V
4
25
0.1
10
10
µV
OS
S CM
dV /dT
0.03
2.4
µV/°C
µV/V
µV/V
OS
vs Power Supply
Over Temperature
Long-Term Stability
PSRR
V
= +2.7V to +5.5V, V
= 0V
S
CM
V
= +2.7V to +5.5V, V
= 0V
S
CM
(1)
See Note (1)
1
Channel Separation, dc
µV/V
INPUT BIAS CURRENT
Input Bias Current, Inverting Input
I
I
V
V
= V /2
3
50
pA
pA
B
B
CM
CM
S
Noninverting Input
Over Temperature
NOISE
= V /2
3
200
S
Typical Characteristics
Input Voltage Noise, f = 0.1Hz to 10Hz
Input Voltage Noise Density, f = 10kHz
Input Voltage Noise Density, f > 1MHz
Input Current Noise Density, f = 10kHz
e
e
e
i
V
V
V
V
= +5V, V
= +5V, V
= +5V, V
= +5V, V
= 0V
= 0V
= 0V
= 0V
3
µV
PP
n
n
n
n
S
S
S
S
CM
CM
CM
CM
67
5.8
10
nV/√Hz
nV/√Hz
fA/√Hz
INPUT VOLTAGE RANGE
Common-Mode Voltage Range
Common-Mode Rejection Ratio
V
V−
(V+) − 1.8V
V
CM
CMRR
(V−) < V
CM
< (V+) – 1.8V
95
105
dB
INPUT IMPEDANCE
Differential Capacitance
Common-Mode Resistance and Inverting Input
Capacitance
1.1
pF
13
10 || 3
Ω || pF
OPEN-LOOP GAIN
Open-Loop Voltage Gain
A
0.12V < V < (V+) − 0.7V, V = 5V, V
= V /2
110
130
dB
OL
O
S
CM
S
0.12V < V < (V+) − 0.6V, V = 5V, V
= V /2,
O
S
CM
S
110
130
dB
T
= -40°C to +85°C
A
0V < V < (V+) − 0.7V, V = 5V, V
= 0V,
O
S
CM
106
120
dB
(2)
R
= 2kΩ to −5V
P
0V < V < (V+) − 0.6V, V = 5V, V
= 0V,
O
S
CM
106
120
dB
(2)
R
= 2kΩ to −5V , T = -40°C to +85°C
A
P
FREQUENCY RESPONSE
Gain-Bandwidth Product
Slew Rate
C = 50pF
L
GBW
SR
90
80
2
MHz
V/µs
µs
G = +1
V = +5V, 4V Step, G = +1
S
(3)
Settling Time, 0.01%
t
S
(4), (5)
Overload Recovery Time
V
• G = > V
100
ns
IN
S
OUTPUT
Voltage Output Swing from Positive Rail
Voltage Output Swing from Negative Rail
Voltage Output Swing from Positive Rail
Voltage Output Swing from Negative Rail
Output Current
R
= 2kΩ
= 2kΩ
400
80
600
120
600
0
mV
mV
mV
mV
L
L
R
(2)
(2)
R
R
= 2kΩ to −5V
= 2kΩ to −5V
400
−20
P
P
I
See Typical Characteristics
OUT
Short-Circuit Current
I
150
mA
SC
Capacitive Load Drive
C
See Typical Characteristics
40
LOAD
Open-Loop Output Impedance
R
f = 1MHz, I = 0A
Ω
O
O
POWER SUPPLY
Specified Voltage Range
Quiescent Current (per amplifier)
Over Temperature
V
2.7
5.5
V
S
I
I
= 0A
7.5
9.5
mA
mA
Q
O
10
TEMPERATURE RANGE
Specified and Operating Range
Storage Range
−40
−65
+125
+150
°C
°C
Thermal Resistance
MSOP-8
q
JA
150
°C/W
(1)
(2)
300-hour life test at 150°C demonstrated randomly distributed variation approximately equal to measurement repeatability of 1µV.
Tested with output connected only to R , a pulldown resistor connected between V
and −5V, as shown in Figure 5. See also applications section, Achieving
P
OUT
Output Swing to Ground.
(3)
(4)
(5)
Transimpedance frequency of 1MHz.
Time required to return to linear operation.
From positive rail.
4
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SBOS291E − NOVEMBER 2003 − REVISED NOVEMBER 2004
TYPICAL CHARACTERISTICS: V = +2.7V to +5.5V
S
All specifications at T = +25°C, R = 2kΩ connected to V /2, and V
OUT
= V /2, unless otherwise noted.
S
A
L
S
POWER−SUPPLY REJECTION RATIO AND
COMMON−MODE REJECTION vs FREQUENCY
OPEN−LOOP GAIN AND PHASE vs FREQUENCY
Gain
160
140
120
100
80
90
45
0
140
120
100
80
−
−
−
−
−
−
45
Phase
PSRR
CMRR
60
90
60
40
135
180
225
270
40
20
20
0
0
−
−
20
20
0.1
1
10
100
1k
10k 100k 1M 10M 100M
10
100
1k
10k
100k
1M
10M 100M
Frequency (Hz)
Frequency (Hz)
INPUT VOLTAGE NOISE SPECTRAL DENSITY
QUIESCENT CURRENT vs TEMPERATURE
1000
100
10
8
7
6
5
4
3
2
1
0
VS = +5.5V
VS = +2.7V
1
−
−
10
100
1k
10k
100k
1M
10M
40 25
0
25
50
75
100
125
_
Frequency (Hz)
Temperature ( C)
QUIESCENT CURRENT vs SUPPLY VOLTAGE
INPUT BIAS CURRENT vs TEMPERATURE
7
6
5
4
3
2
1
0
1000
100
10
1
−
−
2.7 3.0
3.5
4.0
4.5
5.0
5.5
40 25
0
25
50
75
100
125
_
Supply Voltage (V)
Temperature ( C)
5
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SBOS291E − NOVEMBER 2003 − REVISED NOVEMBER 2004
TYPICAL CHARACTERISTICS: V = +2.7V to +5.5V (continued)
S
All specifications at T = +25°C, R = 2kΩ connected to V /2, and V
= V /2, unless otherwise noted.
S
A
L
S
OUT
INPUT BIAS CURRENT
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
vs INPUT COMMON−MODE VOLTAGE
(V+)
25
20
15
10
5
−
−
(V+)
(V+)
1
2
−
+
IB
_
−
_
_
+25 C 40 C
+125 C
0
−
(V ) +2
−
5
IB
−
−
−
−
10
15
20
25
−
(V ) +1
−
(V )
0
50
100
150
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Output Current (mA)
Input Common−Mode Voltage (V)
SHORT−CIRCUIT CURRENT vs TEMPERATURE
VS = 5V
OFFSET VOLTAGE PRODUCTION DISTRIBUTION
200
150
100
50
+ISC
0
−
ISC
−
50
−
−
100
150
−
−
40 25
0
25
50
75
100
125
−
−
−
−
−
5
25
20
15
10
0
5
10
15
20
25
_
µ
Offset Voltage ( V)
Temperature ( C)
OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
GAIN BANDWIDTH vs POWER SUPPLY VOLTAGE
95
90
85
80
75
70
2.5
3.5
4.5
5.5
−
−
−
−
−
0.10 0.08 0.06 0.04 0.02
0
0.02 0.04 0.06 0.08 0.1
µ
_
Power Supply Voltage (V)
Offset Voltage Drift ( V/ C)
6
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SBOS291E − NOVEMBER 2003 − REVISED NOVEMBER 2004
TYPICAL CHARACTERISTICS: V = +2.7V to +5.5V (continued)
S
All specifications at T = +25°C, R = 2kΩ connected to V /2, and V
OUT
= V /2, unless otherwise noted.
S
A
L
S
TRANSIMPEDANCE AMP CHARACTERISTIC
CDIODE = 100pF
140
130
120
110
100
90
Circuit for Transimpedance Amplifier Characteristic curves on this page.
Ω
RF = 10M
CF
Ω
RF = 1M
CF = 0.5pF
CF = 2pF
CF = 5pF
CF = 18pF
RF
Ω
RF = 100k
80
CSTRAY
70
Ω
RF = 10k
60
50
Ω
RF = 1k
40
OPA380
30
CSTRAY (parasitic) = 0.2pF
CDIODE
20
100
1k
10k
100k
Frequency (Hz)
1M
10M
100M
100M
100M
TRANSIMPEDANCE AMP CHARACTERISTIC
TRANSIMPEDANCE AMP CHARACTERISTIC
CDIODE = 20pF
140
140
130
120
110
100
90
CDIODE = 50pF
Ω
Ω
RF = 10M
RF = 10M
130
120
110
100
90
Ω
RF = 1M
CF = 0.5pF
CF = 1.5pF
CF = 4pF
CF = 12pF
Ω
Ω
RF = 1M
Ω
RF = 100k
RF = 100k
CF = 1pF
CF = 2.5pF
80
80
70
Ω
RF = 10k
Ω
RF = 10k
70
60
60
50
Ω
RF = 1k
Ω
RF = 1k
50
CF = 7pF
40
40
30
CSTRAY (parasitic) = 0.2pF
1k 10k
CSTRAY (parasitic) = 0.2pF
1k 10k
20
100
30
100
100k
1M
10M
100M
100k
1M
10M
Frequency (Hz)
Frequency (Hz)
TRANSIMPEDANCE AMP CHARACTERISTIC
CDIODE = 1pF
TRANSIMPEDANCE AMP CHARACTERISTIC
CDIODE = 10pF
140
130
120
110
100
90
140
130
120
110
100
90
Ω
RF = 10M
Ω
RF = 10M
Ω
Ω
RF = 1M
Ω
Ω
RF = 1M
RF = 100k
CF = 0.5pF
CF = 2pF
RF = 100k
CF = 0.5pF
CF = 1pF
80
80
Ω
RF = 10k
70
Ω
RF = 10k
70
Ω
RF = 1k
60
Ω
RF = 1k
60
50
CF = 5pF
CF = 2.5pF
1M 10M
50
40
CSTRAY (parasitic) = 0.2pF
1k 10k
CSTRAY (parasitic) = 0.2pF
1k 10k
40
100
30
100
100k
100k
1M
10M
100M
Frequency (Hz)
Frequency (Hz)
7
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TYPICAL CHARACTERISTICS: V = +2.7V to +5.5V (continued)
S
All specifications at T = +25°C, R = 2kΩ connected to V /2, and V
OUT
= V /2, unless otherwise noted.
S
A
L
S
SMALL−SIGNAL OVERSHOOT vs LOAD CAPACITANCE
SMALL−SIGNAL OVERSHOOT vs LOAD CAPACITANCE
50
45
40
35
30
25
20
15
10
5
50
45
40
35
30
25
20
15
10
5
2.5pF
2.5pF
Ω
10k
Ω
10k
+5V
+2.5V
RS
VOUT
RS
OPA380
VO UT
OPA380
Ω
C
RP = 2k
C
RF = 2kΩ
−
5V
−
2.5V
No RS
No RS
Ω
RS = 100
Ω
RS = 100
0
0
10
100
1000
10
100
Load Capacitance (pF)
1000
Load Capacitance (pF)
SMALL−SIGNAL STEP RESPONSE
OVERLOAD RECOVERY
3.2pF
Ω
RL = 2k
Ω
50k
VOUT
−
= 5V
VP
+5V
V
OUT
I
IN
1.6mA
Ω
2k
VP = 0V
V
P
IIN
Time (100ns/div)
Time (100ns/div)
LARGE−SIGNAL STEP RESPONSE
CHANNEL SEPARATION vs INPUT FREQUENCY
140
120
100
80
Ω
RL = 2k
2.5pF
Ω
10k
60
2.5V
40
Ω
2k
20
−
2.5V
0
Time (100ns/div)
10
100
1k
10k
100k
1M
10M
100M
Frequency (Hz)
8
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OPERATING VOLTAGE
APPLICATIONS INFORMATION
BASIC OPERATION
OPA380 series op amps are fully specified from 2.7V to
5.5V over a temperature range of −40°C to +125°C.
Parameters that vary significantly with operating
voltages or temperature are shown in the Typical
Characteristics.
The OPA380 is a high-performance transimpedance
amplifier with very low 1/f noise. As a result of its unique
architecture, the OPA380 has excellent long-term input
voltage offset stability—a 300-hour life test at 150°C
demonstrated
randomly
distributed
variation
INTERNAL OFFSET CORRECTION
approximately equal to measurement repeatability of
1µV.
The OPA380 series op amps use an auto-zero topology
with a time-continuous 90MHz op amp in the signal
path. This amplifier is zero-corrected every 100µs using
a proprietary technique. Upon power-up, the amplifier
The OPA380 performance results from an internal
auto-zero amplifier combined with a high-speed
amplifier. The OPA380 has been designed with circuitry
to improve overload recovery and settling time over a
traditional composite approach. It has been specifically
designed and characterized to accommodate circuit
options to allow 0V output operation (see Figure 3).
requires approximately 400µs to achieve specified V
OS
accuracy, which includes one full auto-zero cycle of
approximately 100µs and the start-up time for the bias
circuitry. Prior to this time, the amplifier will function
properly but with unspecified offset voltage.
The OPA380 is used in inverting configurations, with the
noninverting input used as a fixed biasing point.
Figure 1 shows the OPA380 in a typical configuration.
Power-supply pins should be bypassed with 1µF ceramic
or tantalum capacitors. Electrolytic capacitors are not
recommended.
This design has virtually no aliasing and very low noise.
Zero correction occurs at a 10kHz rate, but there is very
little fundamental noise energy present at that
frequency due to internal filtering. For all practical
purposes, any glitches have energy at 20MHz or higher
and are easily filtered, if required. Most applications are
not sensitive to such high-frequency noise, and no
filtering is required.
CF
RF
INPUT VOLTAGE
The input common-mode voltage range of the OPA380
series extends from V− to (V+) –1.8V. With input signals
above this common-mode range, the amplifier will no
longer provide a valid output value, but it will not latch
or invert.
+5V
µ
1 F
λ
(1)
VOUT
(0.5V to 4.4V)
OPA380
INPUT OVERVOLTAGE PROTECTION
V
BIAS = 0.5V
Device inputs are protected by ESD diodes that will
conduct if the input voltages exceed the power supplies
by more than approximately 500mV. Momentary
voltages greater than 500mV beyond the power supply
can be tolerated if the current is limited to 10mA. The
OPA380 series feature no phase inversion when the
inputs extend beyond supplies if the input is current
limited.
NOTE: (1) VOUT = 0.5V in dark conditions.
Figure 1. OPA380 typical configuration
9
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OUTPUT RANGE
ACHIEVING OUTPUT SWING TO GROUND
The OPA380 is specified to swing within at least 600mV
of the positive rail and 100mV of the negative rail with
a 2kΩ load with excellent linearity. Swing to the negative
rail while maintaining good linearity can be extended to
0V—see the section, Achieving Output Swing to
Ground. See the Typical Characteristic curve, Output
Voltage Swing vs Output Current.
Some applications require output voltage swing from
0V to a positive full-scale voltage (such as +4.096V)
with excellent accuracy. With most single-supply op
amps, problems arise when the output signal
approaches 0V, near the lower output swing limit of a
single-supply op amp. A good single-supply op amp
may swing close to single-supply ground, but will not
reach 0V.
The OPA380 can swing slightly closer than specified to
the positive rail; however, linearity will decrease and a
high-speed overload recovery clamp limits the amount
of positive output voltage swing available—see
Figure 2.
The output of the OPA380 can be made to swing to
ground, or slightly below, on a single-supply power
source. This extended output swing requires the use of
another resistor and an additional negative power
supply. A pulldown resistor may be connected between
the output and the negative supply to pull the output
down to 0V. See Figure 3.
OFFSET VOLTAGE vs OUTPUT VOLTAGE
20
VS = 5V
15
10
Ω
−
RP = 2k connected to 5V
RF
5
0
5
λ
V+ = +5V
−
Ω
RL = 2k connected to VS /2
OPA380
VOUT
−
−
−
10
15
20
Effect of clamp
Ω
RP = 2k
−
V
= Gnd
0
1
2
3
4
5
VOUT (V)
−
VP = 5V
Negative Supply
Figure 2. Effect of high-speed overload recovery
clamp on output voltage
Figure 3. Amplifier with optional pull-down
resistor to achieve V = 0V
OUT
OVERLOAD RECOVERY
The OPA380 has been designed to prevent output
saturation. After being overdriven to the positive rail, it
will typically require only 100ns to return to linear
operation. The time required for negative overload
recovery is greater, unless a pulldown resistor
connected to a more negative supply is used to extend
the output swing all the way to the negative rail—see the
following section, Achieving Output Swing to Ground.
The OPA380 has an output stage that allows the output
voltage to be pulled to its negative supply rail using this
technique. However, this technique only works with
some types of output stages. The OPA380 has been
designed to perform well with this method. Accuracy is
excellent down to 0V. Reliable operation is assured over
the specified temperature range.
10
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the desired transimpedance gain (R );
F
BIASING PHOTODIODES IN SINGLE-SUPPLY
CIRCUITS
the Gain Bandwidth Product (GBW) for the
OPA380 (90MHz).
The +IN input can be biased with a positive DC voltage
to offset the output voltage and allow the amplifier
output to indicate a true zero photodiode measurement
when the photodiode is not exposed to any light. It will
also prevent the added delay that results from coming
out of the negative rail. This bias voltage appears
across the photodiode, providing a reverse bias for
faster operation. An RC filter placed at this bias point will
reduce noise. (Refer to Figure 4.) This bias voltage can
also serve as an offset bias point for an ADC with range
that does not include ground.
With these three variables set, the feedback capacitor
value (C ) can be set to control the frequency response.
F
C
is the stray capacitance of R , which is 0.2pF for
STRAY
F
a typical surface-mount resistor.
To achieve a maximally flat 2nd-order Butterworth
frequency response, the feedback pole should be set
to:
GBW
4pRFCTOT
1
+
Ǹ
ǒ
STRAYǓ
2pRF CF ) C
(1)
Bandwidth is calculated by:
(1)
CF
GBW
2pRFCTOT
< 1pF
f*3dB
+
Hz
Ǹ
(2)
RF
These
equations
will
result
in
maximum
Ω
10M
transimpedance bandwidth. For even higher
transimpedance bandwidth, the high-speed CMOS
OPA300 (180MHz GBW), or the OPA656 (230MHz
GBW) may be used.
V+
λ
OPA380
VOUT
For additional information, refer to Application Bulletin
AB−050 (SBOA055), Compensate Transimpedance
Amplifiers Intuitively, available for download at
www.ti.com.
µ
0.1 F
Ω
100k
+VBias
(1)
CF
NOTE: (1) CF is optional to prevent gain peaking.
It includes the stray capacitance of RF.
RF
10MΩ
Figure 4. Filtered reverse bias voltage
(2)
CSTRAY
TRANSIMPEDANCE AMPLIFIER
+5V
Wide bandwidth, low input bias current, and low input
voltage and current noise make the OPA380 an ideal
wideband photodiode transimpedance amplifier. Low
voltage noise is important because photodiode
capacitance causes the effective noise gain of the
circuit to increase at high frequency.
λ
(3)
CTOT
OPA380
VOUT
RP (optional
pulldown resistor)
5V
−
NOTE: (1) CF is optional to prevent gain peaking.
(2) CSTRAY is the stray capacitance of RF
The key elements to a transimpedance design are
shown in Figure 5:
(typically, 0.2pF for a surface−mount resistor).
(3) CTOT is the photodiode capacitance plus OPA380
input capacitance.
the total input capacitance (C
), consisting of the
) plus the parasitic
TOT
photodiode capacitance (C
DIODE
common-mode and differential-mode input
capacitance (3pF + 1.1pF for the OPA380);
Figure 5. Transimpedance Amplifier
11
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SBOS291E − NOVEMBER 2003 − REVISED NOVEMBER 2004
TRANSIMPEDANCE BANDWIDTH AND
NOISE
Ω
RF = 10k
(a)
Limiting the gain set by R can decrease the noise
F
CSTRAY =0.2pF
occurring at the output of the transimpedance circuit.
However, all required gain should occur in the
transimpedance stage, since adding gain after the
transimpedance amplifier generally produces poorer
noise performance. The noise spectral density
λ
OPA380
VOUT
produced by R increases with the square-root of R ,
F
F
whereas the signal increases linearly. Therefore,
signal-to-noise ratio is improved when all the required
gain is placed in the transimpedance stage.
VBIAS
Total noise increases with increased bandwidth. Limit
the circuit bandwidth to only that required. Use a
Ω
RF = 10k
(b)
capacitor, C , across the feedback resistor, R , to limit
F
F
CSTRAY = 0.2pF
CF = 16pF
bandwidth, even if not required for stability if total output
noise is a concern.
Figure 6a shows the transimpedance circuit without any
feedback capacitor. The resulting transimpedance gain
of this circuit is shown in Figure 7. The –3dB point is
approximately 10MHz. Adding a 16pF feedback
capacitor (Figure 6b) will limit the bandwidth and result
in a –3dB point at approximately 1MHz (seen in
Figure 7). Output noise will be further reduced by
λ
OPA380
VOUT
VBIAS
adding a filter (R
and C
) to create a second
FILTER
FILTER
pole (Figure 6c). This second pole is placed within the
feedback loop to maintain the amplifier’s low output
impedance. (If the pole was placed outside the
feedback loop, an additional buffer would be required
and would inadvertently increase noise and dc error).
Ω
RF = 10k
(c)
CSTRAY = 0.2pF
CF = 21pF
Using R
to represent the equivalent diode
DIODE
resistance, and C
plus OPA380 input capacitance, the noise zero, f , is
for equivalent diode capacitance
TOT
Z
RFILTER
calculated by:
Ω
= 100
λ
ǒ
Ǔ
OPA380
RDIODE ) RF
VOUT
fZ
+
CFILTER
= 796pF
ǒ
Ǔ
2pRDIODERF CTOT ) CF
(3)
VBIAS
Figure 6. Transimpedance circuit configurations
with varying total and integrated noise gain
12
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SBOS291E − NOVEMBER 2003 − REVISED NOVEMBER 2004
110
500
400
300
200
100
0
CDIODE = 10pF
CDIODE = 10pF
419µV
See Figure 6a
See Figure 6a
80
50
20
10
−
3dB BW at 1MHz
See Figure 6c
See Figure 6b
See Figure 6c
86µV
30µV
See Figure 6b
10M 100M
−
1
10
100
1k
10k 100k 1M 10M 100M
100
1k
10k
100k
1M
Frequency (Hz)
Frequency (Hz)
Figure 7. Transimpedance gains for circuits in
Figure 6
Figure 9. Integrated output noise for circuits in
Figure 6
Figure 10 shows the effect of diode capacitance on
integrated output noise, using the circuit in Figure 6c.
The effect of these circuit configurations on output noise
is shown in Figure 8 and on integrated output noise in
Figure 9. A 2-pole Butterworth filter (maximally flat in
passband) is created by selecting the filter values using
the equation:
For additional information, refer to Noise Analysis of
FET Transimpedance Amplifiers (SBOA060), and
Noise Analysis for High Speed Op Amps (SBOA066),
available for download from the TI web site.
CFRF + 2CFILTERRFILTER
(4)
with:
f*3dB
79µV
1
2p RFRFILTERCFCFILTER
80
+
CDIODE
= 100pF
Ǹ
(5)
CDIODE
60
0
= 50pF
50µV
35µV
The circuit in Figure 6b rolls off at 20dB/decade. The
circuit with the additional filter shown in Figure 6c rolls
off at 40dB/decade, resulting in improved noise
performance.
CDIODE
= 20pF
30µV
27 V
µ
20
0
CDIODE
= 1pF
CDIODE
= 10pF
See Figure 6c
10 100
300
CDIODE = 10pF
1
1k
10k 100k 1M 10M 100M
Frequency (Hz)
200
Figure 10. Integrated output noise for various
values of C for circuit in Figure 6c
See Figure 6a
DIODE
100
See Figure 6b
See Figure 6c
0
1
10
100
1k
10k 100k
1M
10M 100M
Frequency (Hz)
Figure 8. Output noise for circuits in Figure 6
13
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SBOS291E − NOVEMBER 2003 − REVISED NOVEMBER 2004
One method of improving capacitive load drive in the
unity-gain configuration is to insert a 10Ω to 20Ω
resistor in series with the load. This reduces ringing with
large capacitive loads while maintaining DC accuracy.
BOARD LAYOUT
Minimize photodiode capacitance and stray
capacitance at the summing junction (inverting input).
This capacitance causes the voltage noise of the op
amp to be amplified (increasing amplification at high
frequency). Using a low-noise voltage source to
reverse-bias a photodiode can significantly reduce its
capacitance. Smaller photodiodes have lower
capacitance. Use optics to concentrate light on a small
photodiode.
DRIVING FAST 16-BIT ANALOG-TO-DIGITAL
CONVERTERS (ADC)
The OPA380 series is optimized for driving a fast 16-bit
ADC such as the ADS8411. The OPA380 op amp
buffers the converter’s input capacitance and resulting
charge injection while providing signal gain. Figure 12
shows the OPA380 in a single-ended method of
interfacing the ADS8411 16-bit, 2MSPS ADC. For
additional information, refer to the ADS8411 data sheet.
Circuit board leakage can degrade the performance of
an otherwise well-designed amplifier. Clean the circuit
board carefully. A circuit board guard trace that
encircles the summing junction and is driven at the
same voltage can help control leakage. See Figure 11.
RF
CF
RF
λ
OPA380
VOUT
Ω
15
OPA380
ADS8411
Guard ring
6800pF
Figure 11. Connection of input guard
RC Values shown are optimized for the
ADS8411 values may vary for other ADCs.
OTHER WAYS TO MEASURE SMALL
CURRENTS
Logarithmic amplifiers are used to compress extremely
wide dynamic range input currents to a much narrower
range. Wide input dynamic ranges of 8 decades, or
100pA to 10mA, can be accommodated for input to a
12-bit ADC. (Suggested products: LOG101, LOG102,
LOG104, LOG112.)
Figure 12. Driving 16-bit ADCs
CF
RF
Extremely small currents can be accurately measured
by integrating currents on a capacitor. (Suggested
product: IVC102.)
R1
VIN
Low-level currents can be converted to high-resolution
data words. (Suggested product: DDC112.)
OPA380
VOUT
For further information on the range of products
available, search www.ti.com using the above specific
model names or by using keywords transimpedance
and logarithmic.
(Provides high−speed amplification
with very low offset and drift.)
CAPACITIVE LOAD AND STABILITY
Figure 13. OPA380 inverting gain configuration
The OPA380 series op amps can drive up to 500pF pure
capacitive load. Increasing the gain enhances the
amplifier’s ability to drive greater capacitive loads (see
the Typical Characteristic curve, Small Signal
Overshoot vs Capacitive Load).
14
PACKAGE OPTION ADDENDUM
www.ti.com
9-Dec-2004
PACKAGING INFORMATION
Orderable Device
OPA2380AIDGKR
OPA2380AIDGKT
Status (1)
ACTIVE
ACTIVE
Package Package
Pins Package Eco Plan (2) Lead/Ball Finish MSL Peak Temp (3)
Qty
Type
Drawing
MSOP
DGK
8
2500 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
no Sb/Br)
MSOP
DGK
8
250 Green (RoHS & CU NIPDAU Level-2-260C-1 YEAR
no Sb/Br)
OPA380AID
OPA380AIDGKR
OPA380AIDGKT
OPA380AIDR
ACTIVE
ACTIVE
ACTIVE
ACTIVE
SOIC
MSOP
MSOP
SOIC
D
8
8
8
8
100
2500
250
None
None
None
None
CU SNPB
Level-1-220C-UNLIM
DGK
DGK
D
CU NIPDAU Level-1-220C-UNLIM
CU NIPDAU Level-1-220C-UNLIM
2500
CU SNPB
Level-1-220C-UNLIM
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - May not be currently available - please check http://www.ti.com/productcontent for the latest availability information and additional
product content details.
None: Not yet available Lead (Pb-Free).
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Green (RoHS & no Sb/Br): TI defines "Green" to mean "Pb-Free" and in addition, uses package materials that do not contain halogens,
including bromine (Br) or antimony (Sb) above 0.1% of total product weight.
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDECindustry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 1
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