OPT101_03 BURR-BROWN [Burr-Brown Corporation], OPT101_03 Datasheet - Page 8

• Manufacturer Part Number: OPT101_03
• Description: MONOLITHIC PHOTODIODE AND SINGLE-SUPPLY TRANSIMPEDANCE AMPLIFIER
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

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, I
flux, (in watts) falling on the photodiode. At a wavelength of
650nm (visible red) the photodiode Responsivity, R
approximately 0.45A/W. Responsivity at other wavelengths is
shown in the typical performance curve “Responsivity vs
Wavelength.”
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 5.2mm
The OPT101’s voltage output is the product of the photodiode
current times the feedback resistor, (I
voltage, V
supply operation. The internal feedback resistor is laser trimmed
to 1M . Using this resistor, the output voltage responsivity, R
is approximately 0.45V/ W at 650nm wavelength. Figure 1
shows the basic circuit connections for the OPT101 operating
with a single power supply and using the internal 1M feedback
resistor for a response of 0.45V/ W 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
8
FIGURE 1. Basic Circuit Connections.
B
, of approximately 7.5mV introduced for single
2
Common
8
D
V
, is proportional to the radiant power, or
B
V
S
= +2.7 to +36V
3
1M
1
OPT101
3pF
8pF
0.01 to 0.1 F
D
R
4
Positive going output
5
Dark output
with increased light
F
), plus a pedestal
7.5mV
2
I
.
, is
www.ti.com
V
,
source to sink currents up to approximately 100 A. The
benefits of this current sink are shown in the typical
performance curves “Small Signal Response (C
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 100 A as shown in the typical performance
curve "Quiescent Current vs (V
FIGURE 2. Bipolar Power Supply Circuit Connections.
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 R
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 300 Vrms, or
100 Vrms. 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.
F
2
and measured bandwidth (0.1Hz to the
Common
8
V
B
OPT101
OUT
1M
1
3
–V = –1V to (V
– V
V
S
3pF
8pF
0.01 to 0.1 F
PIN3
)".
0.01 to 0.1 F
4
5
S
– 36V)
OPT101
SBBS002A
LOAD
=