Datasheet OPA380A, OPA380 Datasheet (Texas Instruments)

FEATURES

D > 1MHz TRANSIMPEDANCE BANDWIDTH
D EXCELLENT LONG-TERM V

OS

STABILITY

D BIAS CURRENT: 50pA (max)
D OFFSET VOLTAGE: 25µV (max)
D DYNAMIC RANGE: 4 to 5 Decades
D DRIFT: 0.1µV/°C (max)
D GAIN BANDWIDTH: 90MHz
D QUIESCENT CURRENT: 6.5mA
D SUPPLY RANGE: 2.7V to 5.5V
D SINGLE AND DUAL VERSIONS
D MicroSize PACKAGE: MSOP-8

APPLICATIONS

D PHOTODIODE MONITORING
D PRECISION I/V CONVERSION
D OPTICAL AMPLIFIERS
D CAT-SCANNER FRONT-END

1MΩ

R

F

100kΩ

+5V

7

2

3

4

6

OPA380

67pF

75pF

−5V

R

P

(Optional
Pulldown
Resistor)

V

OUT

(0V to 4.4V)

Photodiode

DESCRIPTION

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.

The signal bandwidth o f a t ransimpedance a mplifier d epends
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 trans­impedance bandwidth of > 1 MHz i n most c onfigurations. The
OPA380 is i deally suited f or f ast c ontrol l oops f or p ower l evel
on an optical fiber.

As a result o f t he h igh p r ecision and l ow-noise c haracteristics
of the OPA380, a dynami c range of 4 to 5 dec ades can be
achieved. For example, this capability allows the
measurement of signal currents on the order of 1nA, and up
to 100µA 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 pull-down resistor to –5V, the output voltage range
can be extended to include 0V.

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 RELATED DEVICES

PRODUCT FEATURES

OPA300 150MHz CMOS, 2.7V to 5.5V Supply
OPA350 500µV VOS, 38MHz, 2.5V to 5V Supply
OPA335 10µV VOS, Zero-Drift, 2.5V to 5V Supply
OPA132 16MHz GBW, Precision FET Op Amp, ±15V
OPA656/7 230MHz, Precision FET, ±5V
LOG112 LOG amp, 7.5 decades, ±4.5V to ±18V Supply
LOG114 LOG amp, 7.5 decades, ±2.25V to ±5.5V Supply
IVC102 Precision Switched Integrator
DDC112 Dual Current Input, 20-Bit ADC

OPA380

OPA2380

SBOS291F − NOVEMBER 2003 − REVISED JUNE 2005

Precision, High-Speed

Transimpedance Amplifier

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Copyright  2003-2005, Texas Instruments Incorporated

All trademarks are the property of their respective owners.

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.

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2

ABSOLUTE MAXIMUM RATINGS

(1)

Voltage Supply +7V. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Signal Input Terminals

(2)

, Voltage −0.5V to ( V + ) + 0.5V. . . . . . . . . .

Current ±10mA. . . . . . . . . . . . . . . . . . . . .

Short-Circuit Current

(3)

Continuous. . . . . . . . . . . . . . . . . . . . . . . . .

Operating Temperature Range −40°C to +125°C. . . . . . . . . . . . . . .

Storage Temperature Range −65°C to +150°C. . . . . . . . . . . . . . . . .

Junction Temperature +150°C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Lead Tem perature (soldering, 10s) +300°C. . . . . . . . . . . . . . . . . . . . .

ESD Rating (Human Body Model) 2000V. . . . . . . . . . . . . . . . . . . . . . .

(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 , an d
functional operation of the device at these or any other conditions
beyond those specified is not implied.

(2)

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.

(3)

Short-circuit to ground; one amplifier per package.

ELECTROSTATIC DISCHARGE SENSITIVITY

This integrated circuit can be damaged by ESD. Texas
Instruments recommends that all integrated circuits be
handled with appropriate precautions. Failure to observe

proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to

complete device failure. Precision integrated circuits may be more
susceptible t o damage because very small parametric changes could
cause the device not to meet its published specifications.

PACKAGE/ORDERING INFORMATION

(1)

PRODUCT PACKAGE-LEAD

PACKAGE

MARKING

OPA380

MSOP-8

AUN

OPA380

SO-8

OPA380A

OPA2380

MSOP-8

BBX

(1)

For the most current package and ordering information, see the
Package Option Addendum at the end of this document, or see
the TI web site at www.ti.com.

PIN ASSIGNMENTS

Top View

1
2
3
4

8
7
6
5

NC

(1)

V+

Out

NC

(1)

NC

(1)

−

In

+In

V

−

OPA380

MSOP-8, SO-8

NOTES: (1) NCindicates no internal connection.

1
2
3
4

8
7
6
5

V+
Out B

−

In B

+In B

Out A

−

In A

+In A

V

−

OPA2380

MSOP-8

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3

ELECTRICAL CHARACTERISTICS: OPA380 (SINGLE), VS = 2.7V to 5.5V

Boldface limits apply over the temperature range, TA = −40°C to +125°C.

All specifications at TA = +25°C, RL = 2kΩ connected to VS/2, and V

OUT

= VS/2, unless otherwise noted.

OPA380

PARAMETER CONDITION

MIN TYP MAX

UNITS

OFFSET VOLTAGE

Input Offset Voltage V

OS

VS = +5V , VCM = 0V 4 25 µV

Drift dVOS/dT 0.03 0.1 µV/°C

vs Power Supply PSRR VS = +2.7V to +5.5V , VCM = 0V 2.4 10 µV/V

Over Temperature VS = +2.7V to +5.5V , VCM = 0V 10 µV/V

Long-Term Stability

(1)

See Note (1)

Channel Separation, dc 1 µV/V

INPUT BIAS CURRENT

Input Bias Current I

B

VCM = VS/2 3 ±50 pA

Over Temperature Typical Characteristics

Input Offset Current I

OS

VCM = VS/2 6 ±100 pA

NOISE

Input Voltage Noise, f = 0.1Hz to 10Hz e

n

VS = +5V , VCM = 0V 3 µV

PP

Input Voltage Noise Density, f = 10kHz e

n

VS = +5V , VCM = 0V 67 nV/√Hz

Input Voltage Noise Density, f > 1MHz e

n

VS = +5V , VCM = 0V 5.8 nV/√Hz

Input Current Noise Density, f = 10kHz i

n

VS = +5V , VCM = 0V 10 fA/√Hz

INPUT VOLTAGE RANGE

Common-Mode Voltage Range V

CM

V− (V+) − 1.8V V

Common-Mode Rejection Ratio CMRR (V−) < VCM < (V+) – 1.8V 100 110 dB
INPUT IMPEDANCE

Differential Capacitance 1.1 pF
Common-Mode Resistance and Inverting Input
Capacitance

1013 || 3 Ω || pF

OPEN-LOOP GAIN
Open-Loop Voltage Gain AOL0.1V < VO < (V+) − 0.7V , VS = 5V , VCM = VS/2 110 130 dB

0.1V < VO < (V+) − 0.6V , VS = 5V , VCM = VS/2,
T

A

= −40°C to +85°C

110 130 dB

0V < VO < (V+) − 0.7V , VS = 5V , VCM = 0V ,

R

P

= 2kΩ to −5V

(2)

106 120 dB

0V < VO < (V+) − 0.6V , VS = 5V , VCM = 0V ,
R

P

= 2kΩ to −5V

(2)

, TA = −40°C to +85°C

106 120 dB

FREQUENCY RESPONSE CL = 50pF
Gain-Bandwidth Product GBW 90 MHz
Slew Rate SR G = +1 80 V/µs
Settling Time, 0.01%

(3)

t

S

VS = +5V, 4V Step, G = +1 2 µs

Overload Recovery Time

(4)(5)

VIN × G = > V

S

100 ns

OUTPUT
Voltage Output Swing from Positive Rail RL = 2kΩ 400 600 mV
Voltage Output Swing from Negative Rail RL = 2kΩ 60 100 mV
Voltage Output Swing from Positive Rail RP = 2kΩ to −5V

(2)

400 600 mV

Voltage Output Swing from Negative Rail RP = 2kΩ to −5V

(2)

−20 0 mV

Output Current I

OUT

See Typical Characteristics

Short-Circuit Current I

SC

150 mA

Capacitive Load Drive C

LOAD

See Typical Characteristics

Open-Loop Output Impedance R

O

f = 1MHz, IO = 0A 40 Ω

POWER SUPPL Y

Specified Voltage Range V

S

2.7 5.5 V

Quiescent Current I

Q

IO = 0A 6.5 8.3 mA

Over Temperature 8.8 mA

TEMPERATURE RANGE

Specified and Operating Range −40 +125 °C
Storage Range −65 +150 °C
Thermal Resistance q

JA

MSOP-8, SO-8 150 °C/W

(1)

300-hour life test at 150°C demonstrated randomly distributed variation approximately equal to measurement repeatability of 1µV.

(2)

Tested with output connected only to R

P

, a pulldown resistor connected between V

OUT

and −5V , as shown in Figure 5. See also applications section, Achieving

Output Swing to Ground.

(3)

Transimpedance frequency of 1MHz.

(4)

Time required to return to linear operation.

(5)

From positive rail.

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4

ELECTRICAL CHARACTERISTICS: OPA2380 (DUAL), VS = 2.7V to 5.5V

Boldface limits apply over the temperature range, TA = −40°C to +125°C.

All specifications at TA = +25°C, RL = 2kΩ connected to VS/2, and V

OUT

= VS/2, unless otherwise noted.

OPA2380

PARAMETER CONDITION

MIN TYP MAX

UNITS

OFFSET VOLTAGE

Input Offset Voltage V

OS

VS = +5V , VCM = 0V 4 25 µV

Drift dVOS/dT 0.03 0.1 µV/°C

vs Power Supply PSRR VS = +2.7V to +5.5V , VCM = 0V 2.4 10 µV/V

Over Temperature VS = +2.7V to +5.5V , VCM = 0V 10 µV/V

Long-Term Stability

(1)

See Note (1)

Channel Separation, dc 1 µV/V

INPUT BIAS CURRENT

Input Bias Current, Inverting Input I

B

VCM = VS/2 3 ±50 pA

Noninverting Input I

B

VCM = VS/2 3 ±200 pA

Over Temperature Typical Characteristics

NOISE

Input Voltage Noise, f = 0.1Hz to 10Hz e

n

VS = +5V , VCM = 0V 3 µV

PP

Input Voltage Noise Density, f = 10kHz e

n

VS = +5V , VCM = 0V 67 nV/√Hz

Input Voltage Noise Density, f > 1MHz e

n

VS = +5V , VCM = 0V 5.8 nV/√Hz

Input Current Noise Density, f = 10kHz i

n

VS = +5V , VCM = 0V 10 fA/√Hz

INPUT VOLTAGE RANGE

Common-Mode Voltage Range V

CM

V− (V+) − 1.8V V

Common-Mode Rejection Ratio CMRR (V−) < VCM < (V+) – 1.8V 95 105 dB
INPUT IMPEDANCE

Differential Capacitance 1.1 pF
Common-Mode Resistance and Inverting Input
Capacitance

1013 || 3 Ω || pF

OPEN-LOOP GAIN
Open-Loop Voltage Gain AOL0.12V < VO < (V+) − 0.7V , VS = 5V , VCM = VS/2 110 130 dB

0.12V < VO < (V+) − 0.6V, VS = 5V , VCM = VS/2,
T

A

= −40°C to +85°C

110 130 dB

0V < VO< (V+) − 0.7V , VS = 5V , VCM = 0V ,

R

P

= 2kΩ to −5V

(2)

106 120 dB

0V < VO < (V+) − 0.6V , VS = 5V , VCM = 0V ,

R

P

= 2kΩ to −5V

(2)

, TA = −40°C to +85°C

106 120 dB

FREQUENCY RESPONSE CL = 50pF
Gain-Bandwidth Product GBW 90 MHz
Slew Rate SR G = +1 80 V/µs
Settling Time, 0.01%

(3)

t

S

VS = +5V, 4V Step, G = +1 2 µs

Overload Recovery Time

(4)(5)

VIN × G = > V

S

100 ns

OUTPUT
Voltage Output Swing from Positive Rail RL = 2kΩ 400 600 mV
Voltage Output Swing from Negative Rail RL = 2kΩ 80 120 mV
Voltage Output Swing from Positive Rail RP = 2kΩ to −5V

(2)

400 600 mV

Voltage Output Swing from Negative Rail RP = 2kΩ to −5V

(2)

−20 0 mV

Output Current I

OUT

See Typical Characteristics

Short-Circuit Current I

SC

150 mA

Capacitive Load Drive C

LOAD

See Typical Characteristics

Open-Loop Output Impedance R

O

f = 1MHz, IO = 0A 40 Ω

POWER SUPPL Y

Specified Voltage Range V

S

2.7 5.5 V

Quiescent Current (per amplifier) I

Q

IO = 0A 7.5 9.5 mA

Over Temperature 10 mA

TEMPERATURE RANGE

Specified and Operating Range −40 +125 °C
Storage Range −65 +150 °C
Thermal Resistance q

JA

MSOP-8 150 °C/W

(1)

300-hour life test at 150°C demonstrated randomly distributed variation approximately equal to measurement repeatability of 1µV.

(2)

Tested with output connected only to R

P

, a pulldown resistor connected between V

OUT

and −5V , as shown in Figure 5. See also applications section, Achieving

Output Swing to Ground.

(3)

Transimpedance frequency of 1MHz.

(4)

Time required to return to linear operation.

(5)

From positive rail.

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5

TYPICAL CHARACTERISTICS: VS = +2.7V to +5.5V

All specifications at TA = +25°C, RL = 2kΩ connected to VS/2, and V

OUT

= VS/2, unless otherwise noted.

140
120
100

80
60
40
20

0

−

20

OPEN−LOOPGAIN AND PHASE vs FREQUENCY

Frequency (Hz)

Open−L oop Gain (dB)

90
45
0

−

45

−

90

−

135

−

180

−

225

−

270

Phase (

_

)

10 100 10M1M10k 100k1k 100M

Gain

Phase

160
140
120
100

80
60
40
20

0

−

20

POWER−SUPPLY REJECTION RATIO AND

COMMON−MODE REJECTION vs FREQUENCY

Frequency (Hz)

PSRR, CMRR (dB)

0.1 1 100k 10M1M1k 10k10 100 100M

PSRR

CMRR

1000

100

10

1

INPUT VOLTAGE NOISE SPECTRAL DENSITY

Frequency (Hz)

Input Voltage Noise (nV/

√

(Hz)

10 100 100k 1M10k1k 10M

8
7
6
5
4
3
2
1
0

QUIESCENT CURRENT vs TEMPERATURE

Temperature (_C)

Quiescent Current (mA)

−40−

25 0 25 50 75 100 125

VS=+2.7V

VS=+5.5V

7

6

5

4

3

2

1

0

QUIESCENT CURRENT vs SUPPLY VOLTAGE

Supply Voltage (V)

QuiescentCurrent(mA)

2.7 3.0 3.5 4.0 4.5 5.0 5.5

1000

100

10

1

INPUT BIAS CURRENT vs TEMPERATURE

Temperature (_C)

Input BiasCurrent(pA)

−

40 100 125

−

25 0 25 50 75

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TYPICAL CHARACTERISTICS: VS = +2.7V to +5.5V (continued)

All specifications at TA = +25°C, RL = 2kΩ connected to VS/2, and V

OUT

= VS/2, unless otherwise noted.

25
20
15
10

5
0

−

5

−

10

−

15

−

20

−

25

INPUT BIAS CURRENT

vs INPUT COMMON−MODE VOLTAGE

Input Common−Mode Voltage (V)

−

I

B

+

I

B

Input Bias Current (pA)

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

OUTPUT VOLTAGE SWING vs OUTPUT CURRENT

+125_C

+25_C−40_C

Output Swing(V)

50 100 1500

(V+)

(V+)−1

(V+)−2

(V−)+2

(V−)+1

(V−)

Output Current (mA)

−

40 100 125

−

250 255075

SHORT−CIRCUIT CURRENT vs TEMPERATURE

Short−Circuit Current(mA)

200

150

100

50

0

−

50

−

100

−

150

Temperature (_C)

VS=5V

+I

SC

−

I

SC

OFFSET VOLTAGE PRODUCTION DISTRIBUTION

Offset Voltage (µV)

−25−20−15−10−

50 5 10152025

Population

OFFSETVOLTAGE DRIFT

PRODUCTION DISTRIBUTION

Offset Voltage Drift (µV/_C)

−

0.10−0.08−0.06−0.04−0.02 0 0.020.040.060.08 0.1

Population

GAIN BANDWIDTH vs POWER SUPPLY VOLTAGE

Gain Bandwidth (MHz)

3.5 4.5 5.52.5

95

90

85

80

75

70

Power Supply Voltage (V)

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TYPICAL CHARACTERISTICS: VS = +2.7V to +5.5V (continued)

All specifications at TA = +25°C, RL = 2kΩ connected to VS/2, and V

OUT

= VS/2, unless otherwise noted.

C

F

Circuit for Transimpedance Amplifier Characteristic curves on this page.

R

F

C

DIODE

OPA380

C

STRAY

TRANSIMPEDANCE AMP CHARACTERISTIC

100

140
130
120
110
100

90
80
70
60
50
40
30
20

1k 10k 100k 1M 10M 100M

Frequency (Hz)

Transimpedance Gain (V/A in dB)

RF=10M

Ω

C

STRAY

(parasitic) = 0.2pF

C

DIODE

= 100pF

RF=1M

Ω

CF=0.5pF

RF=100k

Ω

RF= 10k

Ω

RF=1k

Ω

CF= 2pF

CF= 5pF

CF=18pF

TRANSIMPEDANCE AMP CHARACTERISTIC

100

140
130
120

110

100

90
80
70
60
50
40
30
20

1k 10k 100k 1M 10M 100M

Frequency (Hz)

Transimpedance Gain (V/A in dB)

RF=10M

Ω

RF=1M

Ω

CF=0.5pF

RF=100k

Ω

RF= 10k

Ω

RF=1k

Ω

CF=1.5pF

CF= 4pF

CF=12pF

C

STRAY

(parasitic) = 0.2pF

C

DIODE

= 50pF

TRANSIMPEDANCE AMP CHARACTERISTIC

100

140
130
120
110
100

90
80
70
60
50
40
30

1k 10k 100k 1M 10M 100M

Frequency (Hz)

Transimpedance Gain (V/A in dB)

RF=10M

Ω

RF=1M

Ω

RF=100k

Ω

RF= 10k

Ω

RF=1k

Ω

CF=1pF

CF= 2.5pF

CF= 7pF

C

STRAY

(parasitic) = 0.2pF

C

DIODE

= 20pF

TRANSIMPEDANCE AMP CHARACTERISTIC

100

140
130
120

110

100

90
80
70
60
50
40
30

1k 10k 100k 1M 10M 100M

Frequency (Hz)

Transimpedance Gain (V/A in dB)

RF=10M

Ω

RF=1M

Ω

RF=100k

Ω

RF= 10k

Ω

RF=1k

Ω

CF= 0.5pF

CF= 2pF

CF= 5pF

C

STRAY

(parasitic) = 0.2pF

C

DIODE

=10pF

TRANSIMPEDANCE AMP CHARACTERISTIC

100

140
130
120
110
100

90
80
70
60
50
40

1k 10k 100k 1M 10M 100M

Frequency (Hz)

Transimpedance Gain (V/A in dB)

RF= 10M

Ω

RF=1M

Ω

RF=100k

Ω

RF= 10k

Ω

RF=1k

Ω

CF=0.5pF

CF=1pF

CF=2.5pF

C

STRAY

(parasitic) = 0.2pF

C

DIODE

=1pF

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TYPICAL CHARACTERISTICS: VS = +2.7V to +5.5V (continued)

All specifications at TA = +25°C, RL = 2kΩ connected to VS/2, and V

OUT

= VS/2, unless otherwise noted.

SMALL−SIGNAL OVERSHOOT vsLOAD CAPACITANCE

Overshoot (%)

100 100010

50
45
40
35
30
25
20
15
10

5
0

Load Capacitance (pF)

RS=100

Ω

No R

S

−

5V

V

OUT

RP=2k

Ω

C

R

S

+5V

OPA380

2.5pF

10k

Ω

SMALL−SIGNAL OVERSHOOT vsLOAD CAPACITANCE

Overshoot (%)

100 100010

50
45
40
35
30
25
20
15
10

5
0

Load Capacitance (pF)

RS=100

Ω

No R

S

V

OUT

RF=2kΩC

R

S

+2.5V

−

2.5V

OPA380

2.5pF

10k

Ω

OVERLOAD RECOVERY

00 0.8mA/div 2V/div

Time (100ns/div)

3.2pF

V

P

V

OUT

2k

Ω

50k

Ω

+5V

I

IN

1.6mA

VP=0V

VP=−5V

V

OUT

I

IN

SMALL−SIGNAL STEP RESPONSE

50mV/div

Time(100ns/div)

RL=2k

Ω

LARGE−SIGNAL STEP RESPONSE

1V/div

Time(100ns/div)

RL=2k

Ω

10k

Ω

2.5V

−

2.5V

2k

Ω

2.5pF

CHANNEL SEPARATION vs INPUT FREQUENCY

10

140

120

100

80

60

40

20

0

100 1k 10k 100k 1M 10M 100M

Frequency (Hz)

Channel Separation (dB)

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9

APPLICATIONS INFORMATION

BASIC OPERATION

The OPA380 is a high-performance transimpedance
amplifier with very low 1/f noise. As a result of its unique
architecture, the OP A380 has excellent long-term input
voltage offset stability—a 300-hour life test at 150°C
demonstrated randomly distributed variation
approximately equal to measurement repeatability of
1µV.

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).

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.

OPA380

V

OUT

(1)

(0.5V to 4.4V)

V

BIAS

=0.5V

+5V

1µF

R

F

C

F

λ

NOTE: (1) V

OUT

= 0.5V in dark conditions.

Figure 1. OPA380 Typical Configuration

OPERATING VOLTAGE

The 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.

INTERNAL OFFSET CORRECTION

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
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.

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.

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.

INPUT OVERVOLTAGE PROTECTION

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.

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10

OUTPUT RANGE

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.

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, as shown in
Figure 2.

20
15
10

5
0

−

5

−

10

−

15

−

20

OFFSET VOLTAGEvs OUTPUT VOLTAGE

V

OUT

(V)

V

OS

(

µ

V)

012345

V

S

=5V

RP=2kΩconnected to−5V

RL=2kΩconnected to VS/2

Effect of clamp

Figure 2. Effect of High-Speed Overload

Recovery Clamp on Output Voltage

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 pull-down 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.

ACHIEVING OUTPUT SWING TO GROUND

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 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 pull-down resistor may be connected between
the output and the negative supply to pull the output
down to 0V. See Figure 3.

OPA380 V

OUT

R

F

RP=2k

Ω

V+ = +5V

V−=Gnd

V

P

=−5V

Negative Supply

λ

Figure 3. Amplifier with Optional Pull-Down

Resistor to Achieve V

OUT

= 0V

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.

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11

BIASING PHOTODIODES IN SINGLE-SUPPLY
CIRCUITS

The +IN input can be biased with a positive DC voltage
to offset the output voltage and allow the amplifier
output to ind icate 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, as shown in Figure 4. This bias voltage
can also serve as an offset bias point for an ADC with
range that does not include ground.

OPA380 V

OUT

100k

Ω

V+

R

F

10M

Ω

C

F

(1)

<1pF

0.1µF

λ

NOTE: (1) C

F

is optional to prevent gain peaking.

It includes the stray capacitance of R

F

.

+V

Bias

Figure 4. Filtered Reverse Bias Voltage

TRANSIMPEDANCE AMPLIFIER

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.

The key elements to a transimpedance design are
shown in Figure 5:

the total input capacitance (C

TOT

), consisting of the

photodiode capacitance (C

DIODE

) plus the parasitic
common-mode and differential-mode input
capacitance (3pF + 1.1pF for the OPA380);

the desired transimpedance gain (R

F

);

the Gain Bandwidth Product (GBW) for the
OPA380 (90MHz).

With these three variables set, the feedback capacitor
value (C

F

) can be set to control the frequency response.

C

STRAY

is the stray capacitance of RF, which is 0.2pF for

a typical surface-mount resistor.
To achieve a maximally flat, 2nd-order, Butterworth

frequency response, the feedback pole should be set
to:

1

2pR

F

ǒ

CF) C

STRAY

Ǔ

+

GBW

4pRFC

TOT

Ǹ

Bandwidth is calculated by:

f

*3dB

+

GBW

2pRFC

TOT

Ǹ

Hz

These equations will result in maximum
transimpedance bandwidth. For even higher
transimpedance bandwidth, the high-speed CMOS
OPA300 (SBOS271 (180MHz GBW)), or the OPA656
(SBOS196 (230MHz GBW)) may be used.

For additional information, refer to Application Bulletin
AB−050 (SBOA055), Compensate Transimpedance
Amplifiers Intuitively, available for download at

www.ti.com.

C

TOT

(3)

OPA380 V

OUT

−

5V

10MΩ

+5V

R

F

C

F

(1)

C

STRAY

(2)

λ

NOTE: (1) C

F

is optional to prevent gain peaking.

(2) C

STRAY

is the stray capacitance of R

F

(typically, 0.2pF for a surface−mountresistor).

(3) C

TOT

is the photodiode capacitance plus OPA380

input capacitance.

R

P

(optional

pulldown resistor)

Figure 5. Transimpedance Amplifier

(1)

(2)

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12

TRANSIMPEDANCE BANDWIDTH AND
NOISE

Limiting the gain set by RF can decrease the noise
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
produced by RF increases with the square-root of RF,
whereas the signal increases linearly. Therefore,
signal-to-noise ratio is improved when all the required
gain is placed in the transimpedance stage.

Total noise increases with increased bandwidth. Limit
the circuit bandwidth to only that required. Use a
capacitor, CF, across the feedback resistor, RF, to limit
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 (see Figure 7).
Output noise will be further reduced by adding a filter
(R

FILTER

and C

FILTER

) to create a second 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).

Using R

DIODE

to represent the equivalent diode

resistance, and C

TOT

for equivalent diode capacitance
plus OPA380 input capacitance, the noise zero, fZ, is
calculated by:

f

Z

+

ǒ

R

DIODE

) R

F

Ǔ

2pR

DIODE

R

F

ǒ

C

TOT

) C

F

Ǔ

OPA380

V

OUT

V

BIAS

RF=10k

Ω

(a)

λ

C

STRAY

=0.2pF

CF=16pF

OPA380

V

OUT

V

BIAS

RF= 10k

Ω

(b)

λ

C

STRAY

=0.2pF

V

OUT

C

FILTER

= 796pF

R

FILTER

= 100

Ω

CF= 21pF

OPA380

V

BIAS

RF=10k

Ω

(c)

λ

C

STRAY

=0.2pF

Figure 6. Transimpedance Circuit Configurations

with Varying Total and Integrated Noise Gain

(3)

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13

110

80

50

20

−

10

Frequency (Hz)

Transimpedance Gain (dB)

100 10k1k 1M 10M100k 100M

−

3dB BW at 1MHz

SeeFigure6a

C

DIODE

= 10pF

SeeFigure6c

SeeFigure6b

Figure 7. Transimpedance Gains for Circuits in

Figure 6

The effect of these circuit configurations o n 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:

CFRF+ 2C

FILTERRFILTER

with:

f

*3dB

+

1

2p RFR

FILTERCFCFILTER

Ǹ

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.

300

200

100

0

Frequency (Hz)

Output Noise (nV/

√

Hz)

C

DIODE

= 10pF

SeeFigure6a

See Figure 6b

SeeFigure6c

110010 10k1k 1M 10M100k 100M

Figure 8. Output Noise for Circuits in Figure 6

500

400

300

200

100

0

Frequency (Hz)

110010 10k1k 1M 10M100k 100M

419µV

30µV

86µV

C

DIODE

= 10pF

See Figure 6a

SeeFigure 6b

SeeFigure6c

Integrated Output Noise (µV

rms

)

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.

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.

80

60

0

20

0

Frequency (Hz)

1 10010 10k1k 1M 10M100k 100M

C

DIODE

= 100pF

C

DIODE

= 10pF

C

DIODE

= 1pF

See Figure 6c

C

DIODE

= 50pF

50µV

35µV

30µV

27µV

79µV

C

DIODE

= 20pF

Integrated Output Noise (µV

rms

)

Figure 10. Integrated Output Noise for Various

Values of C

DIODE

for Circuit in Figure 6c

(4)

(5)

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14

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.

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, as shown in
Figure 11.

Guard Ring

R

F

V

OUT

OPA380

λ

Figure 11. Connection of Input Guard

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, and LOG112.)

Extremely small currents can be accurately measured
by integrating currents on a capacitor. (Suggested
product: IVC102.)

Low-level currents can be converted to high-resolution
data words. (Suggested product: DDC112.)

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.

CAPACITIVE LOAD AND STABILITY

The OP A380 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).

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.

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.

OPA380

R

F

15

Ω

6800pF

ADS8411

C

F

RC Values shown are optimized for the

ADS8411values may vary for other ADCs.

Figure 12. Driving 16-Bit ADCs

OPA380

R

F

R

1

(Provides high−speed amplification
with very low offset and drift.)

V

OUT

C

F

V

IN

Figure 13. OPA380 Inverting Gain Configuration

PACKAGING INFORMATION

Orderable Device Status

(1)

Package

Type

Package

Drawing

Pins Package

Qty

Eco Plan

(2)

Lead/Ball Finish MSL Peak Temp

(3)

OPA2380AIDGKR ACTIVE MSOP DGK 8 2500 Green (RoHS &

no Sb/Br)

CU NIPDAU Level-2-260C-1 YEAR

OPA2380AIDGKRG4 ACTIVE MSOP DGK 8 2500 Green(RoHS &

no Sb/Br)

CU NIPDAU Level-2-260C-1 YEAR

OPA2380AIDGKT ACTIVE MSOP DGK 8 250 Green (RoHS &

no Sb/Br)

CU NIPDAU Level-2-260C-1 YEAR

OPA2380AIDGKTG4 ACTIVE MSOP DGK 8 250 Green (RoHS &

no Sb/Br)

CU NIPDAU Level-2-260C-1 YEAR

OPA380AID ACTIVE SOIC D 8 100 Green (RoHS &

no Sb/Br)

CU NIPDAU Level-2-260C-1 YEAR

OPA380AIDG4 ACTIVE SOIC D 8 100 Green (RoHS &

no Sb/Br)

CU NIPDAU Level-2-260C-1 YEAR

OPA380AIDGKR ACTIVE MSOP DGK 8 2500 Green(RoHS &

no Sb/Br)

CU NIPDAU Level-2-260C-1 YEAR

OPA380AIDGKRG4 ACTIVE MSOP DGK 8 2500 Green (RoHS &

no Sb/Br)

CU NIPDAU Level-2-260C-1 YEAR

OPA380AIDGKT ACTIVE MSOP DGK 8 250 Green (RoHS &

no Sb/Br)

CU NIPDAU Level-2-260C-1 YEAR

OPA380AIDGKTG4 ACTIVE MSOP DGK 8 250 Green (RoHS &

no Sb/Br)

CU NIPDAU Level-2-260C-1 YEAR

OPA380AIDR ACTIVE SOIC D 8 2500 Green (RoHS &

no Sb/Br)

CU NIPDAU Level-2-260C-1 YEAR

OPA380AIDRG4 ACTIVE SOIC D 8 2500 Green (RoHS &

no Sb/Br)

CU NIPDAU Level-2-260C-1 YEAR

(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 - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check

http://www.ti.com/productcontent for the latest availability information and additional product content details.

TBD: The Pb-Free/Green conversion plan has not been defined.
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.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and
package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS
compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)

(3)

MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry 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
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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.

PACKAGE OPTION ADDENDUM

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18-Jul-2006

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to Customer on an annual basis.

PACKAGE OPTION ADDENDUM

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