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Dual/Quad Rail-to-Rail Operational Amplifiers OP295/OP495
FEATURES
Rail-to-rail output swing Single-supply operation: 3 V to 36 V Low offset voltage: 300 V Gain bandwidth product: 75 kHz High open-loop gain: 1000 V/mV Unity-gain stable Low supply current/per amplifier: 150 A maximum
PIN CONFIGURATIONS
OUT A -IN A +IN A V-
1 2 3 4 8
V+ OUT B
00331-001
00331-004
TOP VIEW (Not to Scale)
OP295
7 6 5
-IN B +IN B
Figure 1. 8-Lead Narrow-Body SOIC_N (S Suffix)
APPLICATIONS
Battery-operated instrumentation Servo amplifiers Actuator drives Sensor conditioners Power supply control
OUT A -IN A +IN A V-
1 2 3 4
OP295
8 7 6 5
V+ OUT B
00331-002 00331-003
-IN B +IN B
Figure 2. 8-Lead PDIP (P Suffix)
GENERAL DESCRIPTION
Rail-to-rail output swing combined with dc accuracy are the key features of the OP495 quad and OP295 dual CBCMOS operational amplifiers. By using a bipolar front end, lower noise and higher accuracy than those of CMOS designs have been achieved. Both input and output ranges include the negative supply, providing the user with zero-in/zero-out capability. For users of 3.3 V systems such as lithium batteries, the OP295/OP495 are specified for 3 V operation. Maximum offset voltage is specified at 300 V for 5 V operation, and the open-loop gain is a minimum of 1000 V/mV. This yields performance that can be used to implement high accuracy systems, even in single-supply designs. The ability to swing rail-to-rail and supply 15 mA to the load makes the OP295/OP495 ideal drivers for power transistors and H bridges. This allows designs to achieve higher efficiencies and to transfer more power to the load than previously possible without the use of discrete components. For applications such as transformers that require driving inductive loads, increases in efficiency are also possible. Stability while driving capacitive loads is another benefit of this design over CMOS rail-to-rail amplifiers. This is useful for driving coax cable or large FET transistors. The OP295/OP495 are stable with loads in excess of 300 pF.
OUT A -IN A +IN A V+ +IN B -IN B OUT B
1 2 3 4 5 6 7
14 13 12
OUT D -IN D +IN D V- +IN C -IN C OUT C
OP495
11 10 9 8
Figure 3. 14-Lead PDIP (P Suffix)
OUT A -IN A +IN A V+ +IN B -IN B OUT B NC
1 2 3 4 5 6 7 8
16 15
OUT D -IN D +IN D V- +IN C -IN C OUT C NC
TOP VIEW (Not to Scale)
OP495
14 13 12 11 10 9
NC = NO CONNECT
Figure 4. 16-Lead SOIC_W (S Suffix)
The OP295 and OP495 are specified over the extended industrial (-40C to +125C) temperature range. The OP295 is available in 8-lead PDIP and 8-lead SOIC_N surface-mount packages. The OP495 is available in 14-lead PDIP and 16-lead SOIC_W surface-mount packages.
Rev. E
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c)2006 Analog Devices, Inc. All rights reserved.
OP295/OP495 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications....................................................................................... 1 General Description ......................................................................... 1 Pin Configurations ........................................................................... 1 Revision History ............................................................................... 2 Specifications..................................................................................... 3 Electrical Characteristics............................................................. 3 Absolute Maximum Ratings............................................................ 5 Thermal Resistance ...................................................................... 5 ESD Caution.................................................................................. 5 Typical Performance Characteristics ............................................. 6 Applications....................................................................................... 9 Rail-to-Rail Application Information........................................ 9 Low Drop-Out Reference ............................................................ 9 Low Noise, Single-Supply Preamplifier ..................................... 9 Driving Heavy Loads ................................................................. 10 Direct Access Arrangement ...................................................... 10 Single-Supply Instrumentation Amplifier .............................. 10 Single-Supply RTD Thermometer Amplifier ......................... 11 Cold Junction Compensated, Battery-Powered Thermocouple Amplifier .......................................................... 11 5 V Only, 12-Bit DAC That Swings 0 V to 4.095 V.................... 11 4 to 20 mA Current-Loop Transmitter.................................... 12 3 V Low Dropout Linear Voltage Regulator............................. 12 Low Dropout, 500 mA Voltage Regulator with Foldback Current Limiting ........................................................................ 12 Square Wave Oscillator.............................................................. 13 Single-Supply Differential Speaker Driver.............................. 13 High Accuracy, Single-Supply, Low Power Comparator ...... 13 Outline Dimensions ....................................................................... 14 Ordering Guide .......................................................................... 16
REVISION HISTORY
5/06--Rev. D to Rev. E Updated Format..................................................................Universal Changes to Features.......................................................................... 1 Changes to Pin Connections........................................................... 1 Updated Outline Dimensions ....................................................... 14 Changes to Ordering Guide .......................................................... 15 2/04--Rev. C to Rev. D Changes to General Description .................................................... 1 Changes to Specifications ................................................................ 2 Changes to Absolute Maximum Ratings ....................................... 4 Changes to Ordering Guide ............................................................ 4 Updated Outline Dimensions ....................................................... 12 3/02--Rev. B to Rev. C Figure changes to Pin Connections ................................................1 Deleted OP295GBC and OP495GBC from Ordering Guide ......3 Deleted Wafer Test Limits Table......................................................3 Changes to Absolute Maximum Ratings........................................4 Deleted Dice Characteristics............................................................4
Rev. E | Page 2 of 16
OP295/OP495 SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
VS = 5.0 V, VCM = 2.5 V, TA = 25C, unless otherwise noted. Table 1.
Parameter INPUT CHARACTERISTICS Offset Voltage Input Bias Current Input Offset Current Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain Offset Voltage Drift OUTPUT CHARACTERISTICS Output Voltage Swing High Symbol VOS -40C TA +125C IB -40C TA +125C IOS -40C TA +125C VCM CMRR AVO VOS/T VOH RL = 100 k to GND RL = 10 k to GND IOUT = 1 mA, -40C TA +125C RL = 100 k to GND RL = 10 k to GND IOUT = 1 mA, -40C TA +125C 4.98 4.90 0 V VCM 4.0 V, -40C TA +125C RL = 10 k, 0.005 VOUT 4.0 V RL = 10 k, -40C TA +125C 0 90 1000 500 110 10,000 1 5.0 4.94 4.7 0.7 0.7 90 18 110 150 0.03 75 86 1.5 51 <0.1 5 1 8 Conditions Min Typ 30 Max 300 800 20 30 3 5 4.0 Unit A A nA nA nA nA V dB V/mV V/mV V/C V V V mV mV mV mA dB dB A V/s kHz Degrees V p-p nV/Hz pA/Hz
Output Voltage Swing Low
VOL
2 2
Output Current POWER SUPPLY Power Supply Rejection Ratio Supply Current per Amplifier DYNAMIC PERFORMANCE Skew Rate Gain Bandwidth Product Phase Margin NOISE PERFORMANCE Voltage Noise Voltage Noise Density Current Noise Density
IOUT PSRR ISY SR GBP O en p-p en in 1.5 V VS 15 V 1.5 V VS 15 V, -40C TA +125C VOUT = 2.5 V, RL = , -40C TA +125C RL = 10 k
11 90 85
0.1 Hz to 10 Hz f = 1 kHz f = 1 kHz
VS = 3.0 V, VCM = 1.5 V, TA = 25C, unless otherwise noted. Table 2.
Parameter INPUT CHARACTERISTICS Offset Voltage Input Bias Current Input Offset Current Input Voltage Range Common-Mode Rejection Ration Large Signal Voltage Gain Offset Voltage Drift Symbol VOS IB IOS VCM CMRR AVO VOS/T Conditions Min Typ 100 8 1 0 V VCM 2.0 V, -40C TA +125C RL = 10 k 0 90 110 750 1 Max 500 20 3 2.0 Unit V nA nA V dB V/mV V/C
Rev. E | Page 3 of 16
OP295/OP495
Parameter OUTPUT CHARACTERISTICS Output Voltage Swing High Output Voltage Swing Low POWER SUPPLY Power Supply Rejection Ratio Supply Current per Amplifier DYNAMIC PERFORMANCE Slew Rate Gain Bandwidth Product Phase Margin NOISE PERFORMANCE Voltage Noise Voltage Noise Density Current Noise Density Symbol VOH VOL PSRR ISY SR GBP O en p-p en in Conditions RL = 10 k to GND RL = 10 k to GND 1.5 V VS 15 V 1.5 V VS 15 V, -40C TA +125C VOUT = 1.5 V, RL = , -40C TA +125C RL = 10 k Min 2.9 0.7 90 85 110 150 0.03 75 85 1.6 53 <0.1 2 Typ Max Unit V mV dB dB A V/s kHz Degrees V p-p nV/Hz pA/Hz
0.1 Hz to 10 Hz f = 1 kHz f = 1 kHz
VS = 15.0 V, TA = 25C, unless otherwise noted. Table 3.
Parameter INPUT CHARACTERISTICS Offset Voltage Input Bias Current Input Offset Current Input Voltage Range Common-Mode Rejection Ratio Large Signal Voltage Gain Offset Voltage Drift OUTPUT CHARACTERISTICS Output Voltage Swing High Output Voltage Swing Low Output Current POWER SUPPLY Power Supply Rejection Ratio Supply Current per Amplifier Supply Voltage Range DYNAMIC PERFORMANCE Slew Rate Gain Bandwidth Product Phase Margin NOISE PERFORMANCE Voltage Noise Voltage Noise Density Current Noise Density Symbol VOS IB IOS VCM CMRR AVO VOS/T VOH VOL IOUT PSRR ISY VS SR GBP O en p-p en in VS = 1.5 V to 15 V VS = 1.5 V to 15 V, -40C TA +125C VO = 0 V, RL = , VS = 18 V, -40C TA +125C -40C TA +125C VCM = 0 V VCM = 0 V, -40C TA +125C VCM = 0 V VCM = 0 V, -40C TA +125C -15.0 V VCM +13.5 V, -40C TA +125C RL = 10 k -15 90 1000 Conditions Min Typ 300 7 1 Max 500 800 20 30 3 5 +13.5 Unit V V nA nA nA nA V dB V/mV V/C V V V V mA dB dB A V V/s kHz Degrees V p-p nV/Hz pA/Hz
110 4000 1
RL = 100 k to GND RL = 10 k to GND RL = 100 k to GND RL = 10 k to GND
14.95 14.80 -14.95 -14.85 15 90 85 3 ( 1.5) 25 110 175 36 ( 18) 0.03 85 83 1.25 45 <0.1
RL = 10 k
0.1 Hz to 10 Hz f = 1 kHz f = 1 kHz
Rev. E | Page 4 of 16
OP295/OP495 ABSOLUTE MAXIMUM RATINGS
Table 4.
Parameter1 Supply Voltage Input Voltage Differential Input Voltage2 Output Short-Circuit Duration Storage Temperature Range P, S Package Operating Temperature Range OP295G, OP495G Junction Temperature Range P, S Package Lead Temperature (Soldering, 60 sec)
1 2
Rating 18 V 18 V 36 V Indefinite -65C to +150C
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
THERMAL RESISTANCE
-40C to +125C -65C to +150C 300C
JA is specified for worst case mounting conditions; that is, JA is specified for device in socket for PDIP; JA is specified for device soldered to printed circuit board for SOIC package. Table 5. Thermal Resistance
Package Type 8-Lead PDIP (P Suffix) 8-Lead SOIC_N (S Suffix) 14-Lead PDIP (P Suffix) 16-Lead SOIC_W (S Suffix) JA 103 158 83 98 JC 43 43 39 30 Unit C/W C/W C/W C/W
Absolute maximum ratings apply to packaged parts, unless otherwise noted. For supply voltages less than 18 V, the absolute maximum input voltage is equal to the supply voltage.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
Rev. E | Page 5 of 16
OP295/OP495 TYPICAL PERFORMANCE CHARACTERISTICS
140
200 175 150
BASED ON 600 OP AMPS
VS = 5V TA = 25C
120
SUPPLY CURRENT (A)
100
VS = 36V
125 UNITS
00331-005
VS = 5V 80 VS = 3V 60
100 75 50
40
25 0 -250 -200 -150 -100
-25
0
25
50
75
100
-50
0
50
100
150
200
250
TEMPERATURE (C)
INPUT OFFSET VOLTAGE (V)
Figure 5. Supply Current Per Amplifier vs. Temperature
+ OUTPUT SWING (V)
15.2 15.0 14.8 14.6 14.4 14.2 RL = 2k
Figure 8. OP295 Input Offset (VOS) Distribution
250 225 BASED ON 600 OP AMPS VS = 5V -40C TA +85C
VS = 15V
RL = 100k
RL = 10k
200 175 150
UNITS
125 100
- OUTPUT SWING (V)
-14.4 -14.6 -14.8 -15.0 -15.2 -50 -25 0 25 50 TEMPERATURE (C)
RL = 2k RL = 10k RL = 100k
00331-006
75 50 25
100
00331-009
00331-010
0
75
0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
3.2
TCVOS (V/C)
Figure 6. Output Voltage Swing vs. Temperature
3.1 VS = 3V 3.0 RL = 100k 2.9 RL = 10k
5.0 5.1 VS = 5V
Figure 9. OP295 TCVOS Distribution
OUTPUT VOLTAGE SWING (V)
OUTPUT VOLTAGE SWING (V)
RL = 100k 4.9 RL = 10k
2.8
4.8
2.7 RL = 2k 2.6
4.7 RL = 2k
4.6
-25
0
25
50
75
100
00331-007
2.5 -50
4.5 -50
-25
0
25
50
75
100
TEMPERATURE (C)
TEMPERATURE (C)
Figure 7. Output Voltage Swing vs. Temperature
Figure 10. Output Voltage Swing vs. Temperature
Rev. E | Page 6 of 16
00331-008
20 -50
OP295/OP495
500 450 400 350 300 UNITS 250 200 150 100 50 -50 0 50 100 150 200 INPUT OFFSET VOLTAGE (V) 250 300
00331-011
BASED ON 1200 OP AMPS
VS = 5V TA = 25C
40 35 30 25 20 15 10 5 0 -50 VS = +5V SOURCE
OUTPUT CURRENT (mA)
SINK VS = 15V SOURCE SINK
-25
0
25
50
75
100
TEMPERATURE (C)
Figure 11. OP495 Input Offset (VOS) Distribution
500 450 400 350 300
UNITS OPEN-LOOP GAIN (V/V)
Figure 14. Output Current vs. Temperature
100 VS = 15V VO = 10V
BASED ON 1200 OP AMPS
VS = 5V -40C TA +85C
250 200 150 100 50
00331-012
10
RL = 100k
RL = 10k
RL = 2k
0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
3.2
-25
0
25
50
75
100
TCVOS (V/C)
TEMPERATURE (C)
Figure 12. OP495 TCVOS Distribution
20 VS = 5V 16
OPEN-LOOP GAIN (V/V)
10 12
Figure 15. Open-Loop Gain vs. Temperature
VS = 5V VO = 4V
INPUT BIAS CURRENT (nA)
8 RL = 100k 6 RL = 10k 4 RL = 2k 2
12
8
4
00331-033
-25
0 25 50 TEMPERATURE (C)
75
100
-25
0
25
50
75
100
TEMPERATURE (C)
Figure 13. Input Bias Current vs. Temperature
Figure 16. Open-Loop Gain vs. Temperature
Rev. E | Page 7 of 16
00331-015
0 -50
0 -50
00331-014
0
1 -50
00331-013
0 -100
OP295/OP495
VS = 5V TA = 25C 1V
OUTPUT VOLTAGE TO RAIL
100mV
SOURCE
10mV SINK 1mV
10A
100A 1mA LOAD CURRENT
10mA
Figure 17. Output Voltage to Supply Rail vs. Load Current
00331-016
100V 1A
Rev. E | Page 8 of 16
OP295/OP495 APPLICATIONS
RAIL-TO-RAIL APPLICATION INFORMATION
The OP295/OP495 have a wide common-mode input range extending from ground to within about 800 mV of the positive supply. There is a tendency to use the OP295/OP495 in buffer applications where the input voltage could exceed the commonmode input range. This can initially appear to work because of the high input range and rail-to-rail output range. But above the common-mode input range, the amplifier is, of course, highly nonlinear. For this reason, there must be some minimal amount of gain when rail-to-rail output swing is desired. Based on the input common-mode range, this gain should be at least 1.2. R5 and R6 set the gain of 1000, making this circuit ideal for maximizing dynamic range when amplifying low level signals in single-supply applications. The OP295/OP495 provide rail-torail output swings, allowing this circuit to operate with 0 V to 5 V outputs. Only half of the OP295/OP495 is used, leaving the other uncommitted op amp for use elsewhere.
0.1F
LED
R1 Q2 2N3906 3 5 Q1 1 R7 510 C1 1500pF R3 R8 100 R4
3
10F + -
LOW DROP-OUT REFERENCE
The OP295/OP495 can be used to gain up a 2.5 V or other low voltage reference to 4.5 V for use with high resolution ADCs that operate from 5 V only supplies. The circuit in Figure 18 supplies up to 10 mA. Its no-load drop-out voltage is only 20 mV. This circuit supplies over 3.5 mA with a 5 V supply.
16k 5V 0.001F 5V 20k
2
VIN
2
MAT03 Q2
7
6 R5 10k
1
R6 10 C2 10F VOUT
2
- +
8
4
OP295/OP495
R2 27k
Figure 19. Low Noise Single-Supply Preamplifier
10 1F TO 10F VOUT = 4.5V +
00331-017
- +
REF43
4
6
1/2 OP295/OP495
Figure 18. 4.5 V, Low Drop-Out Reference
LOW NOISE, SINGLE-SUPPLY PREAMPLIFIER
Most single-supply op amps are designed to draw low supply current at the expense of having higher voltage noise. This tradeoff may be necessary because the system must be powered by a battery. However, this condition is worsened because all circuit resistances tend to be higher; as a result, in addition to the op amp's voltage noise, Johnson noise (resistor thermal noise) is also a significant contributor to the total noise of the system. The choice of monolithic op amps that combine the characteristics of low noise and single-supply operation is rather limited. Most single-supply op amps have noise on the order of 30 nV/Hz to 60 nV/Hz, and single-supply amplifiers with noise below 5 nV/Hz do not exist. To achieve both low noise and low supply voltage operation, discrete designs may provide the best solution. The circuit in Figure 19 uses the OP295/OP495 rail-to-rail amplifier and a matched PNP transistor pair--the MAT03--to achieve zeroin/zero-out single-supply operation with an input voltage noise of 3.1 nV/Hz at 100 Hz.
The input noise is controlled by the MAT03 transistor pair and the collector current level. Increasing the collector current reduces the voltage noise. This particular circuit was tested with 1.85 mA and 0.5 mA of current. Under these two cases, the input voltage noise was 3.1 nV/Hz and 10 nV/Hz, respectively. The high collector currents do lead to a tradeoff in supply current, bias current, and current noise. All of these parameters increase with increasing collector current. For example, typically the MAT03 has an hFE = 165. This leads to bias currents of 11 A and 3 A, respectively. Based on the high bias currents, this circuit is best suited for applications with low source impedance such as magnetic pickups or low impedance strain gauges. Furthermore, a high source impedance degrades the noise performance. For example, a 1 k resistor generates 4 nV/Hz of broadband noise, which is already greater than the noise of the preamp. The collector current is set by R1 in combination with the LED and Q2. The LED is a 1.6 V Zener diode that has a temperature coefficient close to that of the Q2 base-emitter junction, which provides a constant 1.0 V drop across R1. With R1 equal to 270 , the tail current is 3.7 mA and the collector current is half that, or 1.85 mA. The value of R1 can be altered to adjust the collector current. When R1 is changed, R3 and R4 should also be adjusted. To maintain a common-mode input range that includes ground, the collectors of the Q1 and Q2 should not go above 0.5 V; otherwise, they could saturate. Thus, R3 and R4 must be small enough to prevent this condition. Their values and the overall performance for two different values of R1 are summarized in Table 6.
Rev. E | Page 9 of 16
00331-018
OP295/OP495
Finally, the potentiometer, R8, is needed to adjust the offset voltage to null it to zero. Similar performance can be obtained using an OP90 as the output amplifier with a savings of about 185 A of supply current. However, the output swing does not include the positive rail, and the bandwidth reduces to approximately 250 Hz. Table 6. Single-Supply Low Noise Preamp Performance
R1 R3, R4 en @ 100 Hz en @ 10 Hz ISY IB Bandwidth Closed-Loop Gain IC = 1.85 mA 270 200 3.15 nV/Hz 4.2 nV/Hz 4.0 mA 11 A 1 kHz 1000 IC = 0.5 mA 1.0 k 910 8.6 nV/Hz 10.2 nV/Hz 1.3 mA 3 A 1 kHz 1000
10 0%
100 90
2V
2V
1ms
Figure 21. H Bridge Outputs
DIRECT ACCESS ARRANGEMENT
The OP295/OP495 can be used in a single-supply direct access arrangement (DAA), as shown in Figure 22. This figure shows a portion of a typical DM capable of operating from a single 5 V supply, and it may also work on 3 V supplies with minor modifications. Amplifier A2 and Amplifier A3 are configured so that the transmit signal, TxA, is inverted by A2 and is not inverted by A3. This arrangement drives the transformer differentially so the drive to the transformer is effectively doubled over a single amplifier arrangement. This application takes advantage of the ability of the OP295/OP495 to drive capacitive loads and to save power in single-supply applications.
390pF
DRIVING HEAVY LOADS
The OP295/OP495 are well suited to drive loads by using a power transistor, Darlington, or FET to increase the current to the load. The ability to swing to either rail can assure that the device is turned on hard. This results in more power to the load and an increase in efficiency over using standard op amps with their limited output swing. Driving power FETs is also possible with the OP295/OP495 because of their ability to drive capacitive loads of several hundred picofarads without oscillating. Without the addition of external transistors, the OP295/OP495 can drive loads in excess of 15 mA with 15 V or +30 V supplies. This drive capability is somewhat decreased at lower supply voltages. At 5 V supplies, the drive current is 11 mA. Driving motors or actuators in two directions in a single-supply application is often accomplished using an H bridge. The principle is demonstrated in Figure 20. From a single 5 V supply, this driver is capable of driving loads from 0.8 V to 4.2 V in both directions. Figure 21 shows the voltages at the inverting and noninverting outputs of the driver. There is a small crossover glitch that is frequency-dependent; it does not cause problems unless used in low distortion applications, such as audio. If this is used to drive inductive loads, diode clamps should be added to protect the bridge from inductive kickback.
5V
37.4k 0.1F RxA 0.0047F 3.3k + - A1 +
OP295/ OP495
20k
20k 475
22.1k 0.1F TxA 20k 750pF 20k 20k 0.033F 1:1
2.5V REF
2N2222 10k 0 VIN 2.5V 5k 1.67V 10k OUTPUTS - + 10k 2N2907 - + 2N2907 2N2222
Figure 22. Direct Access Arrangement
SINGLE-SUPPLY INSTRUMENTATION AMPLIFIER
The OP295/OP495 can be configured as a single-supply instrumentation amplifier, as shown in Figure 23. For this example, VREF is set equal to V+/2, and VO is measured with respect to VREF. The input common-mode voltage range includes ground, and the output swings to both rails.
Figure 20. H Bridge
00331-019
Rev. E | Page 10 of 16
00331-021
OP295/ OP495
- A3 +
-
OP295/ OP495
A2
00331-020
OP295/OP495
V+ + VIN -
3 5
+8 -4
1/2 OP295/ OP495
7
COLD JUNCTION COMPENSATED, BATTERYPOWERED THERMOCOUPLE AMPLIFIER
VO
+ -
1/2 OP295/ OP495
1
6
2
R1 100k VREF
R2 20k
R3 20k
R4 100k
RG VO = 5 + 200k VIN + VREF RG
00331-022
The 150 A quiescent current per amplifier consumption of the OP295/OP495 makes them useful for battery-powered temperature measuring instruments. The K-type thermocouple terminates into an isothermal block where the terminated junctions' ambient temperatures can be continuously monitored and corrected by summing an equal but opposite thermal EMF to the amplifier, thereby canceling the error introduced by the cold junctions.
AD589
ISOTHERMAL BLOCK 1N914 1.235V 24.9k 9V 7.15k 1% 24.9k 1% 24.3k 1% 4.99k 1% 500 10-TURN ZERO ADJUST 475 1% 2.1k 1% + -
(
)
Figure 23. Single-Supply Instrumentation Amplifier
SCALE ADJUST 20k 1.33M
SINGLE-SUPPLY RTD THERMOMETER AMPLIFIER
This RTD amplifier takes advantage of the rail-to-rail swing of the OP295/OP495 to achieve a high bridge voltage in spite of a low 5 V supply. The OP295/OP495 amplifier servos a constant 200 A current to the bridge. The return current drops across the parallel resistors 6.19 k and 2.55 M, developing a voltage that is servoed to 1.235 V, which is established by the AD589 band gap reference. The 3-wire RTD provides an equal line resistance drop in both 100 legs of the bridge, thus improving the accuracy. The AMP04 amplifies the differential bridge signal and converts it to a single-ended output. The gain is set by the series resistance of the 332 resistor plus the 50 potentiometer. The gain scales the output to produce a 4.5 V full scale. The 0.22 F capacitor to the output provides a 7 Hz low-pass filter to keep noise at a minimum.
200 10-TURNS 26.7k 0.5% ZERO ADJ 5V 26.7k 0.5%
7 3 1
Figure 25. Battery-Powered, Cold-Junction Compensated Thermocouple Amplifier
To calibrate, immerse the thermocouple measuring junction in a 0C ice bath and adjust the 500 zero-adjust potentiometer to 0 V out. Then immerse the thermocouple in a 250C temperature bath or oven and adjust the scale-adjust potentiometer for an output voltage of 2.50 V, which is equivalent to 250C. Within this temperature range, the K-type thermocouple is quite accurate and produces a fairly linear transfer characteristic. Accuracy of 3C is achievable without linearization. Even if the battery voltage is allowed to decay to as low as 7 V, the rail-to-rail swing allows temperature measurements to 700C. However, linearization may be necessary for temperatures above 250C, where the thermocouple becomes rather nonlinear. The circuit draws just under 500 A supply current from a 9 V battery.
5 V ONLY, 12-BIT DAC THAT SWINGS 0 V TO 4.095 V
50 332
8 0.22F 6
+ -
4
100 RTD
2
AMP04
5
VO
100 0.5% -
2
1
+
3
1/2 OP295/ OP495
1.235 37.4k
4.5V = 450C 0V = 0C
Figure 26 shows a complete voltage output DAC with wide output voltage swing operating off a single 5 V supply. The serial input, 12-bit DAC is configured as a voltage output device with the 1.235 V reference feeding the current output pin (IOUT) of the DAC. The VREF, which is normally the input, now becomes the output. The output voltage from the DAC is the binary weighted voltage of the reference, which is gained up by the output amplifier such that the DAC has a 1 mV per bit transfer function.
5V
00331-023
2.55M 1%
6.19k AD589 1%
Figure 24. Low Power RTD Amplifier
Rev. E | Page 11 of 16
00331-024
Resistor RG sets the gain of the instrumentation amplifier. Minimum gain is 6 (with no RG). All resistors should be matched in absolute value as well as temperature coefficient to maximize common-mode rejection performance and minimize drift. This instrumentation amplifier can operate from a supply voltage as low as 3 V.
ALUMEL - AL CR CHROMEL K-TYPE THERMOCOUPLE 40.7V/C +
1.5M 1% COLD JUNCTIONS
2-
8 1
VO 5V = 500C 0V = 0C
3+
4
OP295/ OP495
OP295/OP495
5V R1 17.8k 1.23V
3
5V
8
IL < 50mA
VDD
RFB 2 VREF
1 3
5V VO =
1
MJE 350
IOUT
DAC8043
+ -
8
D 4096
(4.096V)
VIN 5V TO 3.2V
+
8 1 4
VO 44.2k 1% + 100F
+ -
3
GND CLK SRI LD
2
4
AD589
4
7
6
5
OP295/ OP495
R4 100k
00331-025
30.9k 1%
2
43k
AD589
TOTAL POWER DISSIPATION = 1.6mW
Figure 26. A 5 V 12-Bit DAC with 0 V to 4.095 Output Swing
Figure 28. 3 V Low Dropout Voltage Regulator
4 TO 20 mA CURRENT-LOOP TRANSMITTER
Figure 27 shows a self-powered 4 to 20 mA current-loop transmitter. The entire circuit floats up from the single-supply (12 V to 36 V) return. The supply current carries the signal within the 4 to 20 mA range. Thus, the 4 mA establishes the baseline current budget within which the circuit must operate. This circuit consumes only 1.4 mA maximum quiescent current, making 2.6 mA of current available to power additional signal conditioning circuitry or to power a bridge circuit.
NULL ADJ SPAN ADJ 10k 10-TURN 100k 10-TURN 1.21M 1%
3 6
Figure 29 shows the regulator's recovery characteristic when its output underwent a 20 mA to 50 mA step current change.
2V
100
50mA STEP CURRENT CONTROL WAVEFORM 20mA
90
REF02
GND
4
2
OUTPUT
+ 5V
10 0%
00331-027
DIGITAL CONTROL
R2 41.2k R3 5k
1000pF 1.235V
1/2 OP295/ OP495
VIN 0V + 3V
182k 1%
2
+ -
8 1 4
-
100 220 12V TO 36V 4mA TO 20mA
20mV
1ms
Figure 29. Output Step Load Current Recovery
1/2 OP295/ OP495
2N1711
LOW DROPOUT, 500 mA VOLTAGE REGULATOR WITH FOLDBACK CURRENT LIMITING
RL 100
00331-026
220pF 100k HP 5082-2800 1% 100 1%
Figure 27. 4 to 20 mA Current Loop Transmitter
Adding a second amplifier in the regulation loop, as shown in Figure 30, provides an output current monitor as well as foldback current limiting protection.
IRF9531 S D + 6V - G 1N4148
7 8
3 V LOW DROPOUT LINEAR VOLTAGE REGULATOR
Figure 28 shows a simple 3 V voltage regulator design. The regulator can deliver 50 mA load current while allowing a 0.2 V dropout voltage. The OP295/OP495 rail-to-rail output swing drives the MJE350 pass transistor without requiring special drive circuitry. At no load, its output can swing less than the pass transistor's base-emitter voltage, turning the device nearly off. At full load, and at low emitter-collector voltages, the transistor beta tends to decrease. The additional base current is easily handled by the OP295/OP495 output. The amplifier servos the output to a constant voltage, which feeds a portion of the signal to the error amplifier.
I (NORM) = 0.5A RSENSE O IO (MAX) = 1A 0.1 1/4W 5V VO 210k 1% +5 A2 -6 45.3k 1% 45.3k 1% 205k 1%
100k 5%
1/2 OP295/ OP495
0.01F
1
1/2 OP295/ OP495
2
+3 124k A1 1% 4 -2
124k 1%
Higher output current, to 100 mA, is achievable at a higher dropout voltage of 3.8 V.
4
6
Figure 30. Low Dropout, 500 mA Voltage Regulator with Foldback Current Limiting
Rev. E | Page 12 of 16
00331-029
REF43
2.5V
00331-028
OP295/OP495
Amplifier A1 provides error amplification for the normal voltage regulation loop. As long as the output current is less than 1 A, the output of Amplifier A2 swings to ground, reversebiasing the diode and effectively taking itself out of the circuit. However, as the output current exceeds 1 A, the voltage that develops across the 0.1 sense resistor forces the output of Amplifier A2 to go high, forward-biasing the diode, which in turn closes the current-limit loop. At this point, the A2's lower output resistance dominates the drive to the power MOSFET transistor, thereby effectively removing the A1 voltage regulation loop from the circuit. If the output current greater than 1 A persists, the current limit loop forces a reduction of current to the load, which causes a corresponding drop in output voltage. As the output voltage drops, the current-limit threshold also drops fractionally, resulting in a decreasing output current as the output voltage decreases, to the limit of less than 0.2 A at 1 V output. This foldback effect reduces the power dissipation considerably during a short circuit condition, thus making the power supply far more forgiving in terms of the thermal design requirements. Small heat sinking on the power MOSFET can be tolerated. The rail-to-rail swing of the OP295 exacts higher gate drive to the power MOSFET, providing a fuller enhancement to the transistor. The regulator exhibits 0.2 V dropout at 500 mA of load current. At 1 A output, the dropout voltage is typically 5.6 V.
V+ 100k 58.7k
3
+ -
8 1
FREQ OUT FOSC = 1 < 350Hz @ V+ = 5V RC
00331-030
2
4
100k
1/2 OP295/ OP495
R
+
C
Figure 31. Square Wave Oscillator Has Stable Frequency Regardless of Supply Changes
90.9k 10k + 2.2F + 10k - + 100k - - + + V+ 20k 20k V+
VIN
1/4 OP295/ OP495
SPEAKER
Figure 32. Single-Supply Differential Speaker Driver
SQUARE WAVE OSCILLATOR
The circuit in Figure 31 is a square wave oscillator (note the positive feedback). The rail-to-rail swing of the OP295/OP495 helps maintain a constant oscillation frequency even if the supply voltage varies considerably. Consider a battery-powered system where the voltages are not regulated and drop over time. The rail-to-rail swing ensures that the noninverting input sees the full V+/2, rather than only a fraction of it. The constant frequency comes from the fact that the 58.7 k feedback sets up Schmitt trigger threshold levels that are directly proportional to the supply voltage, as are the RC charge voltage levels. As a result, the RC charge time, and therefore, the frequency, remain constant independent of supply voltage. The slew rate of the amplifier limits oscillation frequency to a maximum of about 800 Hz at a 5 V supply.
HIGH ACCURACY, SINGLE-SUPPLY, LOW POWER COMPARATOR
The OP295/OP495 make accurate open-loop comparators. With a single 5 V supply, the offset error is less than 300 V. Figure 33 shows the response time of the OP295/OP495 when operating open-loop with 4 mV overdrive. They exhibit a 4 ms response time at the rising edge and a 1.5 ms response time at the falling edge.
1V
100 90
INPUT
(5mV OVERDRIVE @ OP295 INPUT)
OUTPUT
10 0%
00331-032
SINGLE-SUPPLY DIFFERENTIAL SPEAKER DRIVER
Connected as a differential speaker driver, the OP295/OP495 can deliver a minimum of 10 mA to the load. With a 600 load, the OP295/OP495 can swing close to 5 V p-p across the load.
2V
5ms
Figure 33. Open-Loop Comparator Response Time with 5 mV Overdrive
Rev. E | Page 13 of 16
00331-031
1/4 OP295/ OP495
1/4 OP295/ OP495
OP295/OP495 OUTLINE DIMENSIONS
0.400 (10.16) 0.365 (9.27) 0.355 (9.02)
8 1 5
4
0.280 (7.11) 0.250 (6.35) 0.240 (6.10)
PIN 1 0.100 (2.54) BSC 0.210 (5.33) MAX 0.150 (3.81) 0.130 (3.30) 0.115 (2.92) 0.022 (0.56) 0.018 (0.46) 0.014 (0.36) 0.070 (1.78) 0.060 (1.52) 0.045 (1.14) 0.060 (1.52) MAX 0.015 (0.38) MIN
0.325 (8.26) 0.310 (7.87) 0.300 (7.62) 0.195 (4.95) 0.130 (3.30) 0.115 (2.92)
0.015 (0.38) GAUGE PLANE SEATING PLANE 0.430 (10.92) MAX
0.014 (0.36) 0.010 (0.25) 0.008 (0.20)
0.005 (0.13) MIN
COMPLIANT TO JEDEC STANDARDS MS-001-BA CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. CORNER LEADS MAY BE CONFIGURED AS WHOLE OR HALF LEADS.
Figure 34. 8-Lead Plastic Dual In-Line Package [PDIP] (N-8) P Suffix Dimensions shown in inches and (millimeters)
5.00 (0.1968) 4.80 (0.1890)
8 5
4.00 (0.1574) 3.80 (0.1497) 1
6.20 (0.2440)
4 5.80 (0.2284)
1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040)
1.75 (0.0688) 1.35 (0.0532)
0.50 (0.0196) x 45 0.25 (0.0099)
0.51 (0.0201) COPLANARITY SEATING 0.31 (0.0122) 0.10 PLANE
8 0.25 (0.0098) 0 1.27 (0.0500) 0.40 (0.0157) 0.17 (0.0067)
COMPLIANT TO JEDEC STANDARDS MS-012-AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
Figure 35. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body (R-8) S Suffix Dimensions shown in millimeters and (inches)
Rev. E | Page 14 of 16
OP295/OP495
0.775 (19.69) 0.750 (19.05) 0.735 (18.67)
14 1 8
7
0.280 (7.11) 0.250 (6.35) 0.240 (6.10) 0.325 (8.26) 0.310 (7.87) 0.300 (7.62) 0.060 (1.52) MAX 0.015 (0.38) MIN 0.195 (4.95) 0.130 (3.30) 0.115 (2.92)
PIN 1 0.100 (2.54) BSC 0.210 (5.33) MAX 0.150 (3.81) 0.130 (3.30) 0.110 (2.79) 0.022 (0.56) 0.018 (0.46) 0.014 (0.36)
0.015 (0.38) GAUGE PLANE SEATING PLANE 0.430 (10.92) MAX
0.005 (0.13) MIN 0.070 (1.78) 0.050 (1.27) 0.045 (1.14)
0.014 (0.36) 0.010 (0.25) 0.008 (0.20)
COMPLIANT TO JEDEC STANDARDS MS-001-AA CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN. CORNER LEADS MAY BE CONFIGURED AS WHOLE OR HALF LEADS.
Figure 36. 14-Lead Plastic Dual In-Line Package [PDIP] (N-14) P Suffix Dimensions shown in inches and (millimeters)
10.50 (0.4134) 10.10 (0.3976)
16 9
7.60 (0.2992) 7.40 (0.2913)
1 8
10.65 (0.4193) 10.00 (0.3937)
1.27 (0.0500) BSC 0.30 (0.0118) 0.10 (0.0039) COPLANARITY 0.10 0.51 (0.0201) 0.31 (0.0122)
2.65 (0.1043) 2.35 (0.0925)
0.75 (0.0295) x 45 0.25 (0.0098)
SEATING PLANE
8 0.33 (0.0130) 0 0.20 (0.0079)
1.27 (0.0500) 0.40 (0.0157)
COMPLIANT TO JEDEC STANDARDS MS-013-AA CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
Figure 37. 16-Lead Standard Small Outline Package [SOIC_W] Wide Body (RW-16) S Suffix Dimensions shown in millimeters and (inches)
Rev. E | Page 15 of 16
OP295/OP495
ORDERING GUIDE
Model OP295GP OP295GPZ 1 OP295GS OP295GS-REEL OP295GS-REEL7 OP295GSZ1 OP295GSZ-REEL1 OP295GSZ-REEL71 OP495GP OP495GPZ1 OP495GS OP495GS-REEL OP495GSZ1 OP495GSZ-REEL1
1
Temperature Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C -40C to +125C
Package Description 8-Lead Plastic DIP 8-Lead Plastic DIP 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 14-Lead Plastic DIP 14-Lead Plastic DIP 16-Lead SOIC_W 16-Lead SOIC_W 16-Lead SOIC_W 16-Lead SOIC_W
Package Option P-Suffix (N-8) P-Suffix (N-8) S-Suffix (R-8) S-Suffix (R-8) S-Suffix (R-8) S-Suffix (R-8) S-Suffix (R-8) S-Suffix (R-8) P-Suffix (N-14) P-Suffix (N-14) S-Suffix (RW-16) S-Suffix (RW-16) S-Suffix (RW-16) S-Suffix (RW-16)
Z = Pb-free part.
(c)2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. C00331-0-5/06(E)
Rev. E | Page 16 of 16

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