OPT101
FPO 70
FEATURES
●SINGLE SUPPLY: +2.7 to +36V
●PHOTODIODE SIZE: 0.090 x 0.090 inch
●INTERNAL 1MΩ FEEDBACK RESISTOR
●HIGH RESPONSIVITY: 0.45A/W (650nm)
●BANDWIDTH: 14kHz at RF = 1MΩ
●LOW QUIESCENT CURRENT: 120µA
●AVAILABLE IN 8-PIN DIP, 5-PIN SIP, AND
8-LEAD SURFACE MOUNT PACKAGES
●CLEAR OR RED PLASTIC VERSIONS
MONOLITHIC PHOTODIODE AND
SINGLE-SUPPLY TRANSIMPEDANCE AMPLIFIER
1MΩ
OPT101
3pF
8pF
2 (2)
5
4
(5)
(4)
V+
λ
3
(3)
8
(1)
V
B
7.5mV
1
(Pin available
on DIP only.)
(SIP) DIP
SPECTRAL RESPONSIVITY
Wavelength (nm)
200 300 400 500 600 700 800 900 1000 1100
Voltage Output (V/µW)
Using Internal
1MΩ Resistor
Infrared
Red “–R”
Package Versions
Ultraviolet
Blue
Green
Yellow
Red
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Photodiode Responsivity (A/W)
®
APPLICATIONS
●MEDICAL INSTRUMENTATION
●LABORATORY INSTRUMENTATION
●POSITION AND PROXIMITY SENSORS
●PHOTOGRAPHIC ANALYZERS
●BARCODE SCANNERS
●SMOKE DETECTORS
● CURRENCY CHANGERS
DESCRIPTION
The OPT101 is a monolithic photodiode with on-chip
transimpedance amplifier. Output voltage increases
linearly with light intensity. The amplifier is designed
for single or dual power supply operation, making it
ideal for battery operated equipment.
The integrated combination of photodiode and
transimpedance amplifier on a single chip eliminates
the problems commonly encountered in discrete de-
signs such as leakage current errors, noise pick-up and
gain peaking due to stray capacitance. The 0.09 x 0.09
inch photodiode is operated in the photoconductive
mode for excellent linearity and low dark current.
The OPT101 operates from +2.7V to +36V supplies
and quiescent current is only 120µA. It is available in
clear plastic 8-pin DIP, 5-pin SIP and J-formed DIP for
surface mounting. Red plastic versions are also avail-
able with optical filter properties, providing selective
response to wavelengths greater than 580nm. Tem-
perature range is 0°C to 70°C.
International Airport Industrial Park • Mailing Address: PO Box 11400 • Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd. • Tucson, AZ 85706
Tel: (520) 746-1111 • Twx: 910-952-1111 • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
©1994 Burr-Brown Corporation PDS-1257B Printed in U.S.A. August, 1995
®
OPT101 2
SPECIFICATIONS
TA = +25°C, VS = +2.7V to +36V, λ = 650nm, internal 1MΩ feedback resistor, and RL = 10k Ω unless otherwise noted.
PHOTODIODE SPECIFICATIONS
TA = +25°C, VS = +2.7V to +36V unless otherwise noted.
Photodiode of OPT101P
PARAMETER CONDITIONS MIN TYP MAX UNITS
Photodiode Area (0.090 x 0.090in) 0.008 in2
(2.29 x 2.29mm) 5.2 mm2
Current Responsivity 650nm 0.45 A/W
650nm 865 µA/W/cm2
Dark Current VDIODE = 7.5mV 2.5 pA
vs Temperature doubles every 7°C
Capacitance 1200 pF
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes
no responsibility for the use of this information, and all use of such information shall be entirely at the user’s own risk. Prices and specifications are subject to change
without notice. No patent rights or licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant
any BURR-BROWN product for use in life support devices and/or systems.
OPT101P, W
PARAMETER CONDITIONS MIN TYP MAX UNITS
RESPONSIVITY
Photodiode Current 650nm 0.45 A/W
Voltage Output 650nm 0.45 V/µW
vs Temperature 100 ppm/°C
Unit to Unit Variation 650nm ±5%
Nonlinearity(1) FS Output = 24V ±0.01 % of FS
Photodiode Area (0.090 x 0.090in) 0.008 in2
(2.29 x 2.29mm) 5.2 mm2
DARK ERRORS, RTO(2)
Offset Voltage, Output +5 +7.5 +10 mV
vs Temperature ±2.5 µV/°C
vs Power Supply VS = +2.7V to +36V 10 100 µV/V
Voltage Noise, Dark, fB = 0.1Hz to 20kHz VS = +15V, VPIN3 = –15V 300 µVrms
TRANSIMPEDANCE GAIN
Resistor 1MΩ
Tolerance, P ±0.5 ±2%
W±0.5 %
vs Temperature ±50 ppm/°C
FREQUENCY RESPONSE
Bandwidth VOUT = 10Vp-p 14 kHz
Rise Fall Time, 10% to 90% VOUT = 10V Step 28 µs
Settling Time, 0.05% VOUT = 10V Step 160 µs
0.1% 80 µs
1% 70 µs
Overload Recovery 100%, Return to Linear Operation 50 µs
OUTPUT
Voltage Output, High (VS) – 1.3 (VS) – 1.15 V
Capacitive Load, Stable Operation 10 nF
Short-Circuit Current VS = 36V 15 mA
POWER SUPPLY
Operating Voltage Range +2.7 +36 V
Quiescent Current Dark, VPIN3 = 0V 120 240 µA
RL = ∞, VOUT = 10V 220 µA
TEMPERATURE RANGE
Specification 0 +70 °C
Operating 0 +70 °C
Storage –25 +85 °C
Thermal Resistance,
θ
JA 100 °C/W
NOTES: (1) Deviation in percent of full scale from best-fit straight line. (2) Referred to Output. Includes all error sources.
®
OPT101
3
OP AMP SPECIFICATIONS
TA = +25°C, VS = +2.7V to +36V, λ = 650nm, internal 1MΩ feedback resistor, and RL = 10k Ω unless otherwise noted.
MOISTURE SENSITIVITY
AND SOLDERING
Clear plastic does not contain the structural-enhancing fillers
used in black plastic molding compound. As a result, clear
plastic is more sensitive to environmental stress than black
plastic. This can cause difficulties if devices have been stored
in high humidity prior to soldering. The rapid heating during
soldering can stress wire bonds and cause failures. Prior to
soldering, it is recommended that plastic devices be baked-out
at +85°C for 24 hours.
The fire-retardant fillers used in black plastic are not compat-
ible with clear molding compound. The OPT101 plastic
packages cannot meet flammability test, UL-94.
ELECTROSTATIC
DISCHARGE SENSITIVITY
This integrated circuit can be damaged by ESD. Burr-Brown
recommends that all integrated circuits be handled with ap-
propriate 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 to damage because very small parametric
changes could cause the device not to meet its published
specifications.
OPT101 Op Amp(1)
PARAMETER CONDITIONS MIN TYP MAX UNITS
INPUT
Offset Voltage ±0.5 mV
vs Temperature ±2.5 µV/°C
vs Power Supply 10 µV/V
Input Bias Current (–) Input 165 pA
vs Temperature (–) Input 1 pA/°C
Input Impedance
Differential 400 || 5 MΩ || pF
Common-Mode 250 || 35 GΩ || pF
Common-Mode Input Voltage Range Linear Operation 0 to [(VS) – 1] V
Common-Mode Rejection 90 dB
OPEN-LOOP GAIN
Open-loop Voltage Gain 90 dB
FREQUENCY RESPONSE
Gain-Bandwidth Product(2) 2 MHz
Slew Rate 1V/µs
Settling Time 1% 5.8 µs
0.1% 7.7 µs
0.05% 8.0 µs
OUTPUT
Voltage Output, High (VS) – 1.3 (VS) – 1.15 V
Short-Circuit Current VS = +36V 15 mA
POWER SUPPLY
Operating Voltage Range +2.7 +36 V
Quiescent Current Dark, VPIN3 = 0V 120 240 µA
RL ∞, VOUT = 10V 220 µA
NOTES: (1) Op amp specifications provided for information and comparison only. (2) Stable gains ≥ 10V/V.
®
OPT101 4
DICE INFORMATION
4
3
5
1
8
2
NOTE: Pad numbers correspond to pin numbers on DIP package.
Feedback
Resistor
Amplifier
Photodiode Area
0.090 x 0.090 inch
2.29 x 2.29mm
PAD FUNCTION
1V
S
2 –In
3–V
41MΩ Feedback
5 Output
8 Common
MECHANICAL INFORMATION
MILS (0.001") MILLIMETERS
Die Size 150 x 120 3.81 x 3.05
Die Thickness 18 0.51
Min. Pad Size 4 x 4 0.1 x 0.1
Backing None
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATIONS
Supply Voltage (VS to
“Common”
or pin 3) ................................0 to +36V
Output Short-Circuit (to ground)............................................... Continuous
Operating Temperature..................................................... –25°C to +85°C
Storage Temperature ........................................................ –25°C to +85°C
Junction Temperature ...................................................................... +85°C
Lead Temperature (soldering, 10s)................................................ +300°C
(Vapor-Phase Soldering Not Recommended)
PACKAGE DRAWING
MODEL COLOR PACKAGE NUMBER(1)
OPT101P Clear 8-Pin Plastic DIP 006-1
OPT101P-R Red 8-Pin Plastic DIP 006-1
OPT101P-J Clear 8-Lead Surface Mount(2) 006-4
OPT101P-R-J Red 8-Lead Surface Mount(2) 006-4
OPT101W Clear 5-Pin Plastic SIP 321
OPT101W-R Red 5-Pin Plastic SIP 321
NOTE: (1) For detailed drawing and dimension table, please see end of data
sheet, or Appendix D of Burr-Brown IC Data Book. (2) 8-pin DIP with J-formed
leads for surface mounting.
PACKAGE INFORMATION
Top View DIP
V
S
–In
–V
1MΩ Feedback
Common
NC
NC
Output
1
2
3
4
8
7
6
5
(1)
NOTE: (1) Photodiode location.
Top View SIP
Common
V
S
–V
1MΩ Feedback
Output
1
2
3
4
5
(1)
®
OPT101
5
TYPICAL PERFORMANCE CURVES
TA = +25°C, VS = +2.7V to +36V, λ = 650nm, internal 1MΩ feedback resistor, and RL = 10k Ω unless otherwise noted.
VOLTAGE RESPONSIVITY vs RADIANT POWER
Radiant Power (µW)
Output Voltage (V)
0.01 0.1 10 100 1k1
10
1
0.1
0.01
0.001
R
F
= 1MΩ
R
F
= 100kΩ
R
F
= 10MΩ
λ = 650nm
R
F
= 50kΩ
RESPONSE vs INCIDENT ANGLE
Relative Response
Incident Angle (°)
0
1.0
0.8
0.6
0.4
0.2
0±20 ±40 ±60 ±80
θ
Y
θ
X
1.0
0.8
0.6
0.4
0.2
0
θ
Y
θ
X
θ
Y
θ
X
SIP Package
Plastic
DIP Package
DARK V
OUT
vs TEMPERATURE
Temperature (°C)
0 10203040506070
8
7.8
7.6
7.4
7.2
7
Output Voltage (mV)
VOLTAGE RESPONSIVITY vs IRRADIANCE
Irradiance (W/m
2
)
Output Voltage (V)
0.001 0.01 1 10 1000.1
10
1
0.1
0.01
0.001
R
F
= 1MΩ
R
F
= 100kΩ
R
F
= 10MΩ
λ = 650nm
R
F
= 50kΩ
VOLTAGE RESPONSIVITY vs FREQUENCY
Frequency (Hz)
100 1k 10k 100k
10
1
0.1
0.01
0.001
Responsivity (V/µW)
R
F
= 50kΩ, C
EXT
= 56pF
R
F
= 10MΩ
R
F
= 1MΩ
R
F
= 100kΩ, C
EXT
= 33pF
NORMALIZED SPECTRAL RESPONSIVITY
Wavelength (nm)
200 300 400 500 600 700 800 900 1000 1100
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Normalized Current or Voltage Output
Ultraviolet
Blue
Green
Yellow
Red
70°C
25°C
Infrared
650nm
(0.45A/W)
Red “–R”
Package Versions
®
OPT101 6
TYPICAL PERFORMANCE CURVES (CONT)
TA = +25°C, VS = +2.7V to +36V, λ = 650nm, internal 1MΩ feedback resistor, and RL = 10k Ω unless otherwise noted.
QUIESCENT CURRENT vs TEMPERATURE
Temperature (°C)
010203040 6050 70
300
275
250
225
200
175
150
125
100
75
50
Quiescent Current (µA)
V
S
= 15V, V
OUT
– V
PIN3
= 15V
V
S
= +15V, V
OUT
– V
PIN3
= 0V
V
S
= +5V, V
OUT
– V
PIN3
= 0V
V
S
= 5V, V
OUT
– V
PIN3
= 5V
QUIESCENT CURRENT vs (V
OUT
– V
PIN3
)
V
OUT
– V
PIN3
(V)
0 5 10 15 20 25 30 35 40
300
250
200
150
100
50
0
Quiescent Current (µA)
V
S
= 2.7V
V
S
= 36V V
S
= 15V
SHORT CIRCUIT CURRENT vs V
S
V
S
(V)
0 5 10 15 20 25 30 35 40
20
18
16
14
12
10
8
6
4
2
0
Short Circuit Current (mA)
(I
BIAS
-I
DARK
) vs TEMPERATURE
Temperature (°C)
0 10203040506070
180
160
140
120
100
80
60
40
20
0
–20
–40
I
BIAS
-I
DARK
(pA)
1MΩ
OPT101
3pF
I
FEEDBACK
(I
BIAS
-I
DARK
)
λ
8(1)
V
B
I
BIAS
8pF
I
DARK
NOISE EFFECTIVE POWER vs
MEASUREMENT BANDWIDTH, V
S
= +15, V
OUT
– V
PIN3
= 0
Bandwidth (Hz)
10 100 1k 10k 100k 1M
10
–7
10
–8
10
–9
10
–10
10
–11
10
–12
Noise Effective Power (W)
R
F
= 10MΩ
R
F
= 50k || 56pF
R
F
= 100k || 33pF
R
F
= 1MΩ
INTERNAL
OUTPUT NOISE VOLTAGE vs
MEASUREMENT BANDWIDTH, V
S
= +15, V
OUT
– V
PIN3
= 15V
Frequency (Hz)
10 100 1k 10k 100k 1M
1000
100
10
1
0.1
Noise Voltage (µVrms)
R
F
= 50kΩ || 56pF
R
F
= 10MΩR
F
= 1MΩ
INTERNAL
R
F
= 100kΩ || 33pF
®
OPT101
7
TYPICAL PERFORMANCE CURVES (CONT)
TA = +25°C, VS = +2.7V to +36V, λ = 650nm, internal 1MΩ feedback resistor, and RL = 10k Ω unless otherwise noted.
SMALL SIGNAL RESPONSE
LARGE SIGNAL RESPONSE
SMALL SIGNAL RESPONSE (C
LOAD
= 10,000 pF)
(Pin 3 = 0V)
SMALL SIGNAL RESPONSE (C
LOAD
= 10,000 pF)
(Pin 3 = –15V)
®
OPT101 8
source to sink currents up to approximately 100µA. The
benefits of this current sink are shown in the typical
performance curves “Small Signal Response (CLOAD =
10,000pF)” which compare operation with pin 3 grounded
and connected to –15V.
Due to the architecture of this output stage current sink, there
is a slight increase in operating current when there is a voltage
between pin 3 and the output. Depending on the magnitude of
this voltage, the quiescent current will increase by
approximately 100µA as shown in the typical performance
curve "Quiescent Current vs (VOUT – VPIN3)".
APPLICATIONS INFORMATION
Figure 1 shows the basic connections required to operate the
OPT101. Applications with high-impedance power supplies
may require decoupling capacitors located close to the
device pins as shown. Output is 7.5mV dc with no light and
increases with increasing illumination.
Photodiode current, ID, is proportional to the radiant power, or
flux, (in watts) falling on the photodiode. At a wavelength of
650nm (visible red) the photodiode Responsivity, RI, is
approximately 0.45A/W. Responsivity at other wavelengths is
shown in the typical performance curve “Responsivity vs
Wavelength.”
FIGURE 1. Basic Circuit Connections.
1MΩ
OPT101
3pF
2(2)
5
4
(5)
(4)
V
S
= +2.7 to +36V
λ
(3)
3
8(1)
V
B
8pF
1
(Pin available
on DIP only.)
Common
Dark output ≈ 7.5mV
Positive going output
with increased light
0.01 to 0.1µF
The typical performance curve “Output Voltage vs Radiant
Power” shows the response throughout a wide range of
radiant power. The response curve “Output Voltage vs
Irradiance” is based on the photodiode area of 5.2mm2.
The OPT101’s voltage output is the product of the photodiode
current times the feedback resistor, (IDRF), plus a pedestal
voltage, VB, of approximately 7.5mV introduced for single
supply operation. The internal feedback resistor is laser trimmed
to 1MΩ. Using this resistor, the output voltage responsivity, R V,
is approximately 0.45V/µW at 650nm wavelength. Figure 1
shows the basic circuit connections for the OPT101 operating
with a single power supply and using the internal 1MΩ feedback
resistor for a response of 0.45V/µW at 650nm. Pin 3 is
connected to common in this configuration.
CAPACITIVE LOADING
The OPT101 is capable of driving load capacitances of 10nF
without instability. However, dynamic performance with
capacitive loads can be improved by applying a negative
bias voltage to Pin 3 (shown in Figure 2). This negative
power supply voltage allows the output to go negative in
response to the reactive effect of a capacitive load. An
internal JFET connected between pin 5 (output) and pin 3
allows the output to sink current. This current sink capability
can also be useful when driving the capacitive inputs of
some analog-to-digital converters which require the signal
NOISE PERFORMANCE
Noise performance of the OPT101 is determined by the op
amp characteristics, feedback components and photodiode
capacitance. The typical performance curve “Output Noise
Voltage vs Measurement Bandwidth” shows how the noise
varies with RF and measured bandwidth (0.1Hz to the
indicated frequency), when the output voltage minus the
voltage on pin 3 is greater than approximately 50mV. Below
this level, the output stage is powered down, and the effective
bandwidth is decreased. This reduces the noise to
approximately 1/3 the nominal noise value of 300µVrms, or
100µVrms. This enables a low level signal to be resolved.
Noise can be reduced by filtering the output with a cutoff
frequency equal to the signal bandwidth. This will improve
signal-to-noise ratio. Also, output noise increases in proportion
to the square root of the feedback resistance, while responsivity
increases linearly with feedback resistance. Best signal-to-noise
ratio is achieved with large feedback resistance. This comes
with the trade-off of decreased bandwidth.
The noise performance of the photodetector is sometimes
characterized by Noise Effective Power (NEP). This is the
radiant power that would produce an output signal equal to the
noise level. NEP has the units of radiant power (watts), or
Watts/√Hz to convey spectral information about the noise.
The typical performance curve “Noise Effective Power” vs
Measurement Bandwidth" illustrates the NEP for the OPT101.
FIGURE 2. Bipolar Power Supply Circuit Connections.
1MΩ
OPT101
3pF
2(2)
5
4
(5)
(4)
V
S
λ
(3)
3
8(1)
V
B
8pF
1
(Pin available
on DIP only.)
Common –V = –1V to (V
S
– 36V)
0.01 to 0.1µF
0.01 to 0.1µF
®
OPT101
9
1MΩ
OPT101
3pF
2(2)
5
4
V
S
λ
3
8
V
B
8pF
1
R
EXT
C
EXT
1MΩ
OPT101
3pF
2(2)
5
4
(5)
(4)
V
S
λ
(3)
3
8(1)
V
B
8pF
1
R
EXT
C
EXT
This capacitor eliminates gain peaking and prevents
instability. The value of CEXT can be determined from the
table in Figure 4. Values of RF, other than shown in the table,
can be interpolated.
(a)-
Series REXT (for SIP package).
(b)-
External Feedback (for DIP package).
REXT CEXT DC Gain Bandwidth
(MΩ) (pF) (x106V/A) (kHz)
150 2 8
225 3 6
5 10 6 2.5
10 5 11 1.3
50 — 51 0.33
REXT CEXT DC Gain Bandwidth
(MΩ) (pF) (x106V/A) (kHz)
0.05(1) 56 0.05 58
0.1(1) 33 0.1 44
1— 1 23
2 — 2 9.4
5 — 5 3.6
10 — 10 1.8
50 — 50 0.34
Note: (1) May require 1kΩ in series with pin 5 when driving
large capacitances.
FIGURE 4. Changing Responsivity with External Resistor.
FIGURE 3. Dark Error (Offset) Adjustment Circuit.
CHANGING RESPONSIVITY
An external resistor, REXT, can be connected to set a different
voltage responsivity. To increase the responsivity, this resistor
can be placed in series with the internal 1MΩ (Figure 4a), or
with the DIP package, the external resistor can replace the
internal resistor by not connecting pin 4 (Figure 4b). The
second configuration also allows the circuit gain to be
reduced below 106V/A by using external resistors of less
than 1MΩ.
Figure 4 includes tables showing the responsivity and
bandwidth. For values of RF less than 1MΩ, an external
capacitor, CEXT should be connected in parallel with RF.
+15V
–15V –15V
OPA177
1MΩ
OPT101
3pF
2(2)
5
4
(5)
(4)
V
S
λ
(3)
3
8(1)
V
B
8pF
1
(Pin available
on DIP only.)
Common –V
R
1
500kΩ
1/2 REF200
100µA
V
O
Adjust R
1
for V
O
= 0V
with no light.
DARK ERRORS
The dark errors in the specification table include all sources.
The dominant source of dark output voltage is the “pedestal”
voltage applied to the non-inverting input of the op amp.
This voltage is introduced to provide linear operation in the
absence of light falling on the photodiode. Photodiode dark
current is approximately 2.5pA and contributes virtually no
offset error at room temperature. The bias current of the op
amp's summing junction (– input) is approximately 165pA.
The dark current will be subtracted from the amplifier's bias
current, and this residual current will flow through the
feedback resistor creating an offset. The effects of temperature
on this difference current can be seen in the typical
performance curve “(IBIAS – IDARK) vs Temperature.” The
dark output voltage can be trimmed to zero with the optional
circuit shown in Figure 3. A low impedance offset driver (op
amp) should be used to drive pin 8 (DIP) because this node
has signal-dependent currents.
Pin Numbers:
DIP (SIP)
Pin Numbers:
DIP (SIP)
®
OPT101 10
LIGHT SOURCE POSITIONING
The OPT101 is tested with a light source that uniformly
illuminates the full area of the integrated circuit, including
the op amp. Although IC amplifiers are light-sensitive to
some degree, the OPT101 op amp circuitry is designed to
minimize this effect. Sensitive junctions are shielded with
metal, and the photodiode area is very large relative to the op
amp input circuitry.
If your light source is focused to a small area, be sure that
it is properly aimed to fall on the photodiode. A narrowly
focused beam falling on only the photodiode will provide
improved settling times compared to a source that uniformly
illuminates the full area of the die. If a narrowly focused
light source were to miss the photodiode area and fall only
on the op amp circuitry, the OPT101 would not perform
properly. The large 0.09" x 0.09" (2.29mm x 2.29mm)
photodiode area allows easy positioning of narrowly focus-
ed light sources. The photodiode area is easily visible, as it
appears very dark compared to the surrounding active
circuitry.
The incident angle of the light source also effects the
apparent sensitivity in uniform irradiance. For small incident
angles, the loss in sensitivity is simply due to the smaller
effective light gathering area of the photodiode (proportional
to the cosine of the angle). At a greater incident angle, light
is diffracted and scattered by the package. These effects are
shown in the typical performance curve “Responsivity vs
Incident Angle.”
DYNAMIC RESPONSE
Using the internal 1MΩ resistor, the dynamic response of
the photodiode/op amp combination can be modeled as a
simple R • C circuit with a –3dB cutoff frequency of
approximately 14kHz. The R and C values are 1MΩ and
11pF respectively. By using external resistors, with less than
3pF parasitic capacitance, the frequency response can be
improved. An external 1MΩ resistor used in the configuration
shown in Figure 4b will create a 23kHz bandwidth with the
same 106V/A dc transimpedance gain. This yields a rise time
of approximately 15µs (10% to 90%). Dynamic response is
not limited by op amp slew rate. This is demonstrated by the
dynamic response oscilloscope photographs showing virtually
identical large-signal and small-signal response.
Dynamic response will vary with feedback resistor value as
shown in the typical performance curve “Responsivity vs
Frequency.” Rise time (10% to 90%) will vary according to
the –3dB bandwidth produced by a given feedback resistor
value:
where:
tr is the rise time (10% to 90%)
fC is the –3dB bandwidth
LINEARITY PERFORMANCE
The photodiode is operated in the photoconductive mode so
the current output of the photodiode is very linear with
radiant power throughout a wide range. Nonlinearity remains
below approximately 0.05% up to 100µA photodiode current.
The photodiode can produce output currents of 1mA or
greater with high radiant power, but nonlinearity increases
to several percent in this region.
This very linear performance at high radiant power assumes
that the full photodiode area is uniformly illuminated. If the
light source is focused to a small area of the photodiode,
nonlinearity will occur at lower radiant power.
0.35
fC
tr =
FIGURE 5. Three-Wire Remote Light Measurement.
1MΩ
OPT101
3pF
0.01 to
0.1µF
21
5
4
λ
83
V
B
8pF
+2.7 to
+36V
NOTE: Pin Numbers for DIP Package.
V
OUT
®
OPT101
11
FIGURE 6. Differential Light Measurement.
FIGURE 7. LED Output Regulation Circuit.
1MΩ
OPT101
5
4
3pF
+15V
10kΩ
OPA627
3.3nF
100kΩ
REF102 LED
IN4148
270Ω
+15V
4
6
2
+15V
7
–15V
4
10V
0.03µF11kΩ
LED
OPT101
Glass Microscope Slide
Approximately
92% light
available for application.
NOTE: OPT101 Pin Numbers for DIP Package.
≈ 8%
V
B
8pF
2 1
2
3
6
38
1MΩ
OPT101
λV
B
V
01
1MΩ
OPT101
λV
B
V
02
100kΩ
LOG100
100kΩ
1nF
NOTE: OPT101 Pin Numbers for DIP Package.
V
OUT
= K log
10
(V
02
/V
01
)
Log of Ratio Measurement
(Absorbance)
3pF
8pF
2
38
5
4
3pF
8pF
2
51
3
7
14
4
38
1+15V
1+15V
27
4
3
1
85
6
R
G
INA118 V
OUT
= (V
02
– V
01
) 1+
Difference Output
50kΩ
R
G
+15V
–15V
6
9
+15V
–15V