OPT101 Monolithic Photodiode and Single-Supply Transimpedance Amplifier
- SBBS002B January 1994 – June 2015 OPT101
  
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DATA SHEET

OPT101 Monolithic Photodiode and Single-Supply Transimpedance Amplifier

1 Features

Single Supply: 2.7 to 36 V
Photodiode Size: 0.090 inch × 0.090 inch
(2.29 mm × 2.29 mm)
Internal 1-MΩ Feedback Resistor
High Responsivity: 0.45 A/W (650 nm)
Bandwidth: 14 kHz at R_F = 1 MΩ
Low Quiescent Current: 120 μA
Packages: Clear Plastic 8-pin PDIP and J-Lead SOP

2 Applications

Medical Instrumentation
Laboratory Instrumentation
Position and Proximity Sensors
Photographic Analyzers
Barcode Scanners
Smoke Detectors
Currency Changers

3 Description

The OPT101 is a monolithic photodiode with on-chip transimpedance amplifier. The integrated combination of photodiode and transimpedance amplifier on a single chip eliminates the problems commonly encountered in discrete designs, such as leakage current errors, noise pick-up, and gain peaking as a result of stray capacitance. Output voltage increases linearly with light intensity. The amplifier is designed for single or dual power-supply operation.

The 0.09 inch × 0.09 inch (2.29 mm × 2.29 mm) photodiode operates in the photoconductive mode for excellent linearity and low dark current.

The OPT101 operates from 2.7 V to 36 V supplies and quiescent current is only 120 μA. This device is available in clear plastic 8-pin PDIP, and J-lead SOP for surface mounting. The temperature range is 0°C to 70°C.

Device Information⁽¹⁾

PART NUMBER	PACKAGE	BODY SIZE (NOM)
OPT101	PDIP (8)	9.53 mm × 6.52 mm
OPT101	SOP (8)	9.52 mm × 6.52 mm

For all available packages, see the package option addendum at the end of the data sheet.

Block Diagram

Spectral Responsivity

4 Revision History

Changes from A Revision (October 2003) to B Revision

Added Pin Functions, ESD Ratings, Recommended Operating Conditions, and Thermal information tables, and Parameter Measurement Information, Detailed Description, Application and Implementation, Power-Supply Recommendations, Layout, and Device and Documentation Support sections; moved existing sectionsGo
Deleted W version of device from Tolerance parameter of Electrical Characteristics table; W version now obsolete Go
Changed Application Information sectionGo

5 Pin Configuration and Functions

DTL and NTC Packages

8-pin SOP and 8-pin PDIP

Top View

1. Photodiode location.

Pin Functions

PIN		I/O	DESCRIPTION
NO.	NAME	I/O	DESCRIPTION
1	V_S	Power	Power supply of device. Apply 2.7 V to 36 V relative to –V pin.
2	–In	Input	Negative input of op amp and the cathode of the photodiode. Either do not connect, or apply additional op amp feedback.
3	–V	Power	Most negative power supply. Connect to ground or a negative voltage that meets the recommended operating conditions.
4	1MΩ Feedback	Input	Connection to internal feedback network. Typically connect to Output, pin 5.
5	Output	Output	Output of device.
6	NC	—	Do not connect
7	NC	—	Do not connect
8	Common	Input	Anode of the photodiode. Typically, connect to ground.

6 Specifications

6.1 Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted) ⁽¹⁾

		MIN	MAX	UNIT
Supply voltage (V_S to Common pin or –V pin)		0	36	V
Output short-circuit (to ground)		Continuous
Temperature	Operating	–25	85	°C
	Junction		85	°C
	Storage, T_stg	–25	85	°C

(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

6.2 ESD Ratings

			VALUE	UNIT
V_(ESD)	Electrostatic discharge	Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001⁽¹⁾	±2000	V
V_(ESD)	Electrostatic discharge	Charged-device model (CDM), per JEDEC specification JESD22-C101⁽²⁾	±500	V

(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.

(2) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.

6.3 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)

		MIN	MAX	UNIT
POWER SUPPLY
	Operating voltage	2.7	36	V
TEMPERATURE
	Specified	0	70	°C
	Operating	0	70	°C

6.4 Thermal Information

THERMAL METRIC⁽¹⁾		OPT101		UNIT
		DTL (SOP)	NTC (PDIP)
		8 PINS	8 PINS
R_θJA	Junction-to-ambient thermal resistance	138.6	128.2	°C/W
R_θJC(top)	Junction-to-case (top) thermal resistance	96.4	113.1	°C/W
R_θJB	Junction-to-board thermal resistance	126.6	107.0	°C/W
ψ_JT	Junction-to-top characterization parameter	17.8	24.2	°C/W
ψ_JB	Junction-to-board characterization parameter	118.8	105.9	°C/W

(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report, SPRA953.

6.5 Electrical Characteristics

At T_A = 25°C, V_S = 2.7 V to 36 V, λ = 650 nm, internal 1-MΩ feedback resistor, and R_L = 10 kΩ (unless otherwise noted)

PARAMETER		TEST CONDITIONS	MIN	TYP	MAX	UNIT
RESPONSIVITY
	Photodiode current			0.45		A/W
	Voltage output			0.45		V/µW
	Voltage output vs temperature			100		ppm/°C
	Unit-to-unit variation			±5%
	Nonlinearity⁽¹⁾	Full-scale (FS) output = 24 V		±0.01		% of FS
	Photodiode area	0.090 in × 0.090 in		0.008		in²
	Photodiode area	2.29 mm × 2.29 mm		5.2		mm²
DARK ERRORS, RTO⁽²⁾
	Offset voltage, output		5	7.5	10	mV
	Offset voltage vs temperature			±10		µV/°C
	Offset voltage vs power supply	V_S = 2.7 V to 36 V		10	100	µV/V
	Voltage noise, dark	f_B = 0.1 Hz to 20 kHz, V_S = 15 V, V_PIN3 = –15 V		300		µVrms
TRANSIMPEDANCE GAIN
	Resistor			1		MΩ
	Tolerance			±0.5%	±2%
	Tolerance vs temperature			±50		ppm/°C
FREQUENCY RESPONSE
	Bandwidth	V_OUT = 10 V_PP		14		kHz
	Rise and fall time	10% to 90%, V_OUT = 10-V step		28		µs
	Settling time	to 0.05%, V_OUT = 10-V step		160		µs
		to 0.1%, V_OUT = 10-V step		80		µs
		to 1%, V_OUT = 10-V step		70		µs
	Overload recovery	100%, return to linear operation		50		µs
OUTPUT
	Voltage output, high		(V_S) – 1.3	(V_S) – 1.15		V
	Capacitive load, stable operation			10		nF
	Short-circuit current	V_S = 36 V		15		mA
POWER SUPPLY
	Quiescent current	Dark, V_PIN3 = 0 V		120		µA
	Quiescent current	R_L = ∞, V_OUT = 10 V		220		µA

(1) Deviation in percent of full scale from best-fit straight line.

(2) Referred to output. Includes all error sources.

6.6 Electrical Characteristics: Photodiode

At T_A = 25°C and V_S = 2.7 V to 36 V (unless otherwise noted)

	TEST CONDITIONS	MIN	TYP	UNIT
Photodiode area	0.090 in × 0.090 in		0.008	in²
Photodiode area	2.29 mm × 2.29 mm		5.2	mm²
Current responsivity	λ = 650 nm		0.45	A/W
Current responsivity	λ = 650 nm		865	(µA/W)/cm²
Dark current	V_DIODE = 7.5 mV		2.5	pA
Dark current vs temperature	V_DIODE = 7.5 mV	Doubles every 7°C		—
Capacitance			1200	pF

6.7 Electrical Characteristics: Op Amp⁽¹⁾

At T_A = 25°C, V_S = 2.7 V to 36 V, λ = 650 nm, internal 1-MΩ feedback resistor, and R_L = 10 kΩ (unless otherwise noted)

PARAMETER		TEST CONDITIONS	MIN	TYP	UNIT
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	Doubles every 10°C		—
	Input impedance	Differential		400 \|\| 5	MΩ \|\| pF
	Input impedance	Common-mode		250 \|\| 35	GΩ \|\| pF
	Common-mode input voltage range	Linear operation	0 to (V_S – 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			1	V/µs
	Settling time	0.05%		8.0	µs
		0.1%		7.7	µs
		1%		5.8	µs
OUTPUT
	Voltage output, high		(V_S) – 1.3	(V_S) – 1.15	V
	Short-circuit current	V_S = 36 V		15	mA
POWER SUPPLY
	Quiescent current	Dark, V_PIN3 = 0 V		120	µA
	Quiescent current	R_L = ∞, V_OUT = 10 V		220	µA

(1) Op amp specifications provided for information and comparison only.

(2) Stable gains ≥ 10 V/V.

6.8 Typical Characteristics

At T_A = 25°C, V_S = 2.7 V to 36 V, λ = 650 nm, internal 1-MΩ feedback resistor, and R_L = 10 kΩ (unless otherwise noted)

OPT101 tc_norm_spectral_resp_sbbs002.gif

Figure 1. Normalized Spectral Responsivity

OPT101 tc_voltage_resp-irradiance_sbbs002.gif

Figure 3. Voltage Responsivity vs Irradiance

OPT101 tc_resp-incident_angle_sbbs002.gif

Figure 5. Response vs Incident Angle

Figure 7. Quiescent Current vs Temperature

Figure 9. Short-Circuit Current vs V_S

OPT101 tc_output_noise_voltage-bw_sbbs002.gif

V_S = 15 V, V_OUT – V_PIN3 = 15 V

Figure 11. Output Noise Voltage vs Measurement Bandwidth

Figure 13. Small-Signal Response

OPT101 tc_small-signal-resp_0v_sbbs002.gif

C_LOAD = 10,000 pF, pin 3 = 0 V

Figure 15. Small-Signal Response

OPT101 tc_voltage_resp-radiant_pwr_sbbs002.gif

Figure 2. Voltage Responsivity vs Radiant Power

Figure 4. Voltage Responsivity vs Frequency

Figure 6. Dark V_OUT vs Temperature

Figure 8. Quiescent Current vs (V_OUT – V_PIN3)

Figure 10. (I_BIAS – I_DARK) vs Temperature

OPT101 tc_noise_effective_power-bw_sbbs002.gif

V_S = 15 V, V_OUT – V_PIN3 = 15 V

Figure 12. Noise Effective Power vs Measurement Bandwidth

Figure 14. Large-Signal Response

OPT101 tc_small-signal-resp_-15v_sbbs002.gif

C_LOAD = 10,000 pF, Pin 3 = –15 V

Figure 16. Small-Signal Response

7 Parameter Measurement Information

7.1 Light Source Positioning and Uniformity

The OPT101 is tested with a light source that uniformly illuminates the full area of the integrated circuit, including the op amp. Although the silicon of integrated circuit (IC) amplifiers is 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 the 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 only on the photodiode provides improved settling times compared to a source that uniformly illuminates the full area of the die. If a narrowly-focused light source misses the photodiode area and falls only on the op amp circuitry, the OPT101 does not perform properly. The large 0.09-in × 0.09-in (2.29 mm × 2.29 mm) photodiode area allows easy positioning of narrowly-focused light sources. The photodiode area is easily visible because the area 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 Figure 5.

8 Detailed Description

8.1 Overview

The OPT101 is a large-area photodiode integrated with an optimized operational amplifier that makes the OPT101 a small, easy-to-use, light-to-voltage device. The photodiode has a very large measurement area that collects a significant amount of light, and thus allows for high-sensitivity measurements. The photodiode has a wide spectral response with a maximum peak in the infrared spectrum, and a useable range from 300 nm to 1100 nm. The wide power-supply range of 2.7 V to 36 V makes this device useful in a variety of architectures; from all-analog circuits to data conversion base circuits. The on-chip voltage source keeps the amplifier in a good operating region, even at low light levels.

The OPT101 voltage output is the product of the photodiode current times the feedback resistor, (I_DR_F), plus a pedestal voltage, V_B, of approximately 7.5 mV introduced for single-supply operation. Output is 7.5 mV dc with no light, and increases with increasing illumination. Photodiode current, I_D, is proportional to the radiant power, or flux, (in watts) falling on the photodiode. At a wavelength of 650 nm (visible red) the photodiode responsivity, R_I, is approximately 0.45 A/W. Responsivity at other wavelengths is shown in Figure 1. The internal feedback resistor is laser trimmed to 1 MΩ. Using this resistor, the output voltage responsivity, R_V, is approximately 0.45 V/μW at 650-nm wavelength.

See Figure 2 for the response throughout a wide range of radiant power in microwatts. Figure 3 shows the response throughout a wide range of irradiance in watts per square meter.

8.2 Functional Block Diagram

8.3 Feature Description

8.3.1 Dark Performance

The dark errors in the Electrical Characteristics table include all sources. The dominant source of dark output voltage is the pedestal voltage applied to the noninverting 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 2.5 pA, and contributes virtually no offset error at room temperature. The bias current of the op amp summing junction (negative input) is approximately 165 pA. The dark current is subtracted from the amplifier bias current, and this residual current flows through the feedback resistor creating an offset. The effects of temperature on this difference current are seen in Figure 10. The dark output voltage is trimmed to zero with the optional circuit shown in Figure 17. Use a low-impedance offset driver (op amp) to drive pin 8 (Common) because this node has signal-dependent currents.

Figure 17. Dark Error (Offset) Adjustment Circuit

8.3.2 Feedback Network and Dynamic Response

The OPT101 features a feedback network for optimal dynamic response. The dynamic response of the OPT101 is dominated by the feedback network and op amp combination. Using the internal 1-MΩ resistor, the dynamic response of the photodiode and op amp combination can be modeled as a simple RC circuit with a –3-dB cutoff frequency of approximately 14 kHz. The R and C values are 1 MΩ and 11 pF, respectively. To improve the frequency response, use external resistors with less than 3-pF parasitic capacitance. An external 1-MΩ resistor used in the configuration shown in Figure 19 creates a 23-kHz bandwidth with the same 106 V/A dc transimpedance gain. This increased bandwidth yields a rise time of approximately 15 μs (10% to 90%). Dynamic response is not limited by op amp slew rate, as demonstrated in Figure 13 and Figure 14, showing virtually identical large-signal and small-signal response.

Dynamic response varies with feedback network value, as shown in Figure 4. Rise time (10% to 90%) varies as a function of the –3-dB bandwidth produced by the feedback network value shown in Equation 1:

Equation 1. t_r = 0.35 / f_C

where

t_r is the rise time (10% to 90%)
f_C is the –3dB bandwidth

8.3.2.1 Changing Responsivity

To set a different voltage responsivity, connect an external resistor, R_EXT. To increase the responsivity, place this resistor in series with the internal 1-MΩ resistor (Figure 18), or replace the internal resistor with an external resistor by not connecting pin 4 (Figure 19). The second configuration also reduces the circuit gain below 106 V/A when using external resistors that are less than 1 MΩ.

Figure 18. Changing Responsivity with External Resistor in Series with Internal Resistor

Table 1. Responsivity and Bandwidth for Figure 18

R_EXT (MΩ)	C_EXT (pF)	DC Gain (× 10⁶V/A)	Bandwidth (kHz)
1	50	2	8
2	25	3	6
5	10	6	2.5
10	5	11	1.3
50	—	51	0.33

Figure 19. Changing Responsivity with External Resistor Only (Internal Resistor Disabled)

Table 2. Responsivity and Bandwidth for Figure 19

R_EXT (MΩ)	C_EXT (pF)	DC Gain (× 10⁶V/A)	Bandwidth (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

(1) May require 1 kΩ in series with pin 5 when driving large capacitances.

Applications using a feedback resistor significantly larger than the internal 1-MΩ resistor require special consideration. Input bias current of the op amp and dark current of the photodiode increase significantly at higher temperatures. This increase combined with the higher gain (R_F > 1 MΩ) can cause the op amp output to be driven to ground at high temperatures. If this problem occurs, use a positive bias voltage applied to pin 8 to make sure that the op amp output remains in the linear operating region when the photodiode is not exposed to light. Alternatively, use a dual power supply. The output may be negative when sensing dark conditions. Use the information discussed in the Dark Performance section and Figure 10 to analyze the desired configuration.

8.3.3 Noise Performance

Noise performance of the OPT101 is determined by the op amp characteristics, feedback network, photodiode capacitance, and signal level. Figure 11 shows how the noise varies with R_F and measured bandwidth (0.1 Hz to the indicated frequency), when the output voltage minus the voltage on pin 3 (–V) is greater than approximately 50 mV. Below this level, the output stage is powered down, and the effective bandwidth is decreased. This decreased bandwidth reduces the noise to approximately 1/3 the nominal noise value of 300 μVrms, or 100 μVrms. This decreased bandwidth enables a low-level signal to be resolved.

To reduce noise and improve the signal-to-noise ratio, filter the output with a cutoff frequency equal to the signal bandwidth. In addition, output noise increases in proportion to the square root of the feedback resistance, while responsivity increases linearly with feedback resistance. To improve the signal-to-noise ratio performance, use large feedback resistance, if decreased bandwidth is acceptable to the application.

The noise performance of the photodetector is sometimes characterized by noise effective power (NEP), the radiant power that produces an output signal equal to the noise level. NEP has the units of radiant power (watts), or W/√Hz to convey spectral information about the noise. Figure 12 illustrates the NEP for the OPT101.

8.3.4 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 less than approximately 0.05% for photodiode currents less than 100-μA. The photodiode is able to produce output currents of 1 mA 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 occurs at lower radiant power.

8.3.5 Capacitive Load Drive

The OPT101 is capable of driving load capacitances of 10 nF without instability. However, dynamic performance with capacitive loads may improve by applying a negative bias voltage to pin 3 (–V, shown in Figure 20). 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 (–V) allows the output to sink current. This current sink capability is also useful when driving the capacitive inputs of some analog-to-digital converters that require the signal source to sink currents up to approximately 100 μA. The benefits of this current sink are shown in Figure 15 and Figure 16. These figures compare operation with pin 3 (–V) grounded and connected to –15 V.

Figure 20. Bipolar Power-Supply Circuit Connections

Because of the architecture of this output stage current sink, there is a slight increase in operating current when there is a voltage between pin 3 (–V) and the output. Depending on the magnitude of this voltage, the quiescent current increases by approximately 100 μA, as shown in Figure 8.

8.4 Device Functional Modes

The OPT101 has a single functional mode and is operational when the power-supply voltage is greater than 2.7 V. The maximum power supply voltage for the OPT101 is 36 V.