LM134,LM234,LM334
LM134/LM234/LM334 3-Terminal Adjustable Current Sources
Literature Number: SNVS746C
LM134/LM234/LM334
3-Terminal Adjustable Current Sources
General Description
The LM134/LM234/LM334 are 3-terminal adjustable current
sources featuring 10,000:1 range in operating current, excel-
lent current regulation and a wide dynamic voltage range of
1V to 40V. Current is established with one external resistor
and no other parts are required. Initial current accuracy is
±3%. The LM134/LM234/LM334 are true floating current
sources with no separate power supply connections. In ad-
dition, reverse applied voltages of up to 20V will draw only a
few dozen microamperes of current, allowing the devices to
act as both a rectifier and current source in AC applications.
The sense voltage used to establish operating current in the
LM134 is 64mV at 25˚C and is directly proportional to abso-
lute temperature (˚K). The simplest one external resistor
connection, then, generates a current with +0.33%/˚C tem-
perature dependence. Zero drift operation can be obtained
by adding one extra resistor and a diode.
Applications for the current sources include bias networks,
surge protection, low power reference, ramp generation,
LED driver, and temperature sensing. The LM234-3 and
LM234-6 are specified as true temperature sensors with
guaranteed initial accuracy of ±3˚C and ±6˚C, respectively.
These devices are ideal in remote sense applications be-
cause series resistance in long wire runs does not affect
accuracy. In addition, only 2 wires are required.
The LM134 is guaranteed over a temperature range of
−55˚C to +125˚C, the LM234 from −25˚C to +100˚C and the
LM334 from 0˚C to +70˚C. These devices are available in
TO-46 hermetic, TO-92 and SO-8 plastic packages.
Features
nOperates from 1V to 40V
n0.02%/V current regulation
nProgrammable from 1µA to 10mA
nTrue 2-terminal operation
nAvailable as fully specified temperature sensor
n±3% initial accuracy
Connection Diagrams
SO-8
Surface Mount Package
SO-8 Alternative Pinout
Surface Mount Package
00569724
Order Number LM334M or LM334MX
See NS Package Number M08A
00569725
Order Number LM334SM or LM334SMX
See NS Package Number M08A
TO-46
Metal Can Package TO-92 Plastic Package
00569712
VPin is electrically connected to case.
Bottom View
Order Number LM134H,
LM234H or LM334H
See NS Package
Number H03H
00569710
Bottom View
Order Number LM334Z, LM234Z-3 or LM234Z-6
See NS Package Number Z03A
March 2005
LM134/LM234/LM334 3-Terminal Adjustable Current Sources
© 2005 National Semiconductor Corporation DS005697 www.national.com
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
V
+
to V
Forward Voltage
LM134/LM234/LM334 40V
LM234-3/LM234-6 30V
V
+
to V
Reverse Voltage 20V
R Pin to V
Voltage 5V
Set Current 10 mA
Power Dissipation 400 mW
ESD Susceptibility (Note 6) 2000V
Operating Temperature Range (Note
5)
LM134 −55˚C to +125˚C
LM234/LM234-3/LM234-6 −25˚C to +100˚C
LM334 0˚C to +70˚C
Soldering Information
TO-92 Package (10 sec.) 260˚C
TO-46 Package (10 sec.) 300˚C
SO Package
Vapor Phase (60 sec.) 215˚C
Infrared (15 sec.) 220˚C
See AN-450 “Surface Mounting Methods and Their Effect on
Product Reliability” (Appendix D) for other methods of sol-
dering surface mount devices.
Electrical Characteristics (Note 2)
Parameter Conditions LM134/LM234 LM334 Units
Min Typ Max Min Typ Max
Set Current Error, V
+
=2.5V, 10µA I
SET
1mA 3 6 %
(Note 3) 1mA <I
SET
5mA 5 8 %
2µA I
SET
<10µA 8 12 %
Ratio of Set Current to 100µA I
SET
1mA 14 18 23 14 18 26
Bias Current 1mA I
SET
5mA 14 14
AI
SET
100 µA 18 23 18 26
Minimum Operating Voltage 2µA I
SET
100µA 0.8 0.8 V
100µA <I
SET
1mA 0.9 0.9 V
1mA <I
SET
5mA 1.0 1.0 V
Average Change in Set Current 2µA I
SET
1mA
with Input Voltage 1.5 V
+
5V 0.02 0.05 0.02 0.1 %/V
5V V
+
40V 0.01 0.03 0.01 0.05 %/V
1mA <I
SET
5mA
1.5V V5V 0.03 0.03 %/V
5V V40V 0.02 0.02 %/V
Temperature Dependence of 25µA I
SET
1mA 0.96T T 1.04T 0.96T T 1.04T
Set Current (Note 4)
Effective Shunt Capacitance 15 15 pF
Note 1: .“Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional, but do not guarantee specific performance limits.
Note 2: Unless otherwise specified, tests are performed at Tj= 25˚C with pulse testing so that junction temperature does not change during test
Note 3: Set current is the current flowing into the V+pin. For the Basic 2-Terminal Current Source circuit shown on the first page of this data sheet. ISET is
determined by the following formula: ISET = 67.7 mV/RSET (@25˚C). Set current error is expressed as a percent deviation from this amount. ISET increases at
0.336%/˚C @Tj= 25˚C (227 µV/˚C).
LM134/LM234/LM334
www.national.com 2
Electrical Characteristics (Note 2) (Continued)
Note 4: ISET is directly proportional to absolute temperature (˚K). ISET at any temperature can be calculated from: ISET =I
o(T/To) where Iois ISET measured at To
(˚K).
Note 5: For elevated temperature operation, TJmax is:
LM134 150˚C
LM234 125˚C
LM334 100˚C
Thermal Resistance TO-92 TO-46 SO-8
θ
ja
(Junction to
Ambient)
180˚C/W (0.4" leads) 440˚C/W 165˚C/W
160˚C/W (0.125"
leads)
θ
jc
(Junction to Case) N/A 32˚C/W 80˚C/W
Note 6: Human body model, 100pF discharged through a 1.5kresistor.
Electrical Characteristics (Note 2)
Parameter Conditions LM234-3 LM234-6 Units
Min Typ Max Min Typ Max
Set Current Error, V
+
=2.5V, 100µA I
SET
1mA ±1±2%
(Note 3) T
J
= 25˚
Equivalent Temperature Error ±3±C
Ratio of Set Current to 100µA I
SET
1mA 14 18 26 14 18 26
Bias Current
Minimum Operating Voltage 100µA I
SET
1mA 0.9 0.9 V
Average Change in Set Current 100µA I
SET
1mA
with Input Voltage 1.5 V
+
5V 0.02 0.05 0.02 0.01 %/V
5V V
+
30V 0.01 0.03 0.01 0.05 %/V
Temperature Dependence of 100µA I
SET
1mA 0.98T T 1.02T 0.97T T 1.03T
Set Current (Note 4) and
Equivalent Slope Error ±2±3%
Effective Shunt Capacitance 15 15 pF
LM134/LM234/LM334
www.national.com3
Typical Performance Characteristics
Output Impedance
Maximum Slew Rate
Linear Operation
00569730 00569731
Start-Up Transient Response
00569732 00569733
Voltage Across R
SET
(V
R
) Current Noise
00569734 00569735
LM134/LM234/LM334
www.national.com 4
Typical Performance Characteristics (Continued)
Turn-On Voltage Ratio of I
SET
to I
BIAS
00569729 00569703
Application Hints
The LM134 has been designed for ease of application, but a
general discussion of design features is presented here to
familiarize the designer with device characteristics which
may not be immediately obvious. These include the effects
of slewing, power dissipation, capacitance, noise, and con-
tact resistance.
CALCULATING R
SET
The total current through the LM134 (I
SET
) is the sum of the
current going through the SET resistor (I
R
) and the LM134’s
bias current (I
BIAS
), as shown in Figure 1.
A graph showing the ratio of these two currents is supplied
under Ratio of I
SET
to I
BIAS
in the Typical Performance
Characteristics section. The current flowing through R
SET
is
determined by V
R
, which is approximately 214µV/˚K (64
mV/298˚K 214µV/˚K).
Since (for a given set current) I
BIAS
is simply a percentage of
I
SET
, the equation can be rewritten
where n is the ratio of I
SET
to I
BIAS
as specified in the
Electrical Characteristics Section and shown in the graph.
Since n is typically 18 for 2µA I
SET
1mA, the equation can
be further simplified to
for most set currents.
SLEW RATE
At slew rates above a given threshold (see curve), the
LM134 may exhibit non-linear current shifts. The slewing
rate at which this occurs is directly proportional to I
SET
.At
I
SET
= 10µA, maximum dV/dt is 0.01V/µs; at I
SET
= 1mA, the
limit is 1V/µs. Slew rates above the limit do not harm the
LM134, or cause large currents to flow.
THERMAL EFFECTS
Internal heating can have a significant effect on current
regulation for I
SET
greater than 100µA. For example, each
1V increase across the LM134 at I
SET
= 1 mA will increase
junction temperature by 0.4˚C in still air. Output current
(I
SET
) has a temperature coefficient of 0.33%/˚C, so the
change in current due to temperature rise will be (0.4)
(0.33) = 0.132%. This is a 10:1 degradation in regulation
compared to true electrical effects. Thermal effects, there-
fore, must be taken into account when DC regulation is
critical and I
SET
exceeds 100µA. Heat sinking of the TO-46
package or the TO-92 leads can reduce this effect by more
than 3:1.
SHUNT CAPACITANCE
In certain applications, the 15 pF shunt capacitance of the
LM134 may have to be reduced, either because of loading
problems or because it limits the AC output impedance of the
current source. This can be easily accomplished by buffering
the LM134 with an FET as shown in the applications. This
can reduce capacitance to less than 3 pF and improve
00569727
FIGURE 1. Basic Current Source
LM134/LM234/LM334
www.national.com5
Application Hints (Continued)
regulation by at least an order of magnitude. DC character-
istics (with the exception of minimum input voltage), are not
affected.
NOISE
Current noise generated by the LM134 is approximately 4
times the shot noise of a transistor. If the LM134 is used as
an active load for a transistor amplifier, input referred noise
will be increased by about 12dB. In many cases, this is
acceptable and a single stage amplifier can be built with a
voltage gain exceeding 2000.
LEAD RESISTANCE
The sense voltage which determines operating current of the
LM134 is less than 100mV. At this level, thermocouple or
lead resistance effects should be minimized by locating the
current setting resistor physically close to the device. Sock-
ets should be avoided if possible. It takes only 0.7contact
resistance to reduce output current by 1% at the 1 mA level.
SENSING TEMPERATURE
The LM134 makes an ideal remote temperature sensor be-
cause its current mode operation does not lose accuracy
over long wire runs. Output current is directly proportional to
absolute temperature in degrees Kelvin, according to the
following formula:
Calibration of the LM134 is greatly simplified because of the
fact that most of the initial inaccuracy is due to a gain term
(slope error) and not an offset. This means that a calibration
consisting of a gain adjustment only will trim both slope and
zero at the same time. In addition, gain adjustment is a one
point trim because the output of the LM134 extrapolates to
zero at 0˚K, independent of R
SET
or any initial inaccuracy.
This property of the LM134 is illustrated in the accompanying
graph. Line abc is the sensor current before trimming. Line
a'b'c' is the desired output. A gain trim done at T2 will move
the output from b to b' and will simultaneously correct the
slope so that the output at T1 and T3 will be correct. This
gain trim can be done on R
SET
or on the load resistor used
to terminate the LM134. Slope error after trim will normally
be less than ±1%. To maintain this accuracy, however, a low
temperature coefficient resistor must be used for R
SET
.
A 33 ppm/˚C drift of R
SET
will give a 1% slope error because
the resistor will normally see about the same temperature
variations as the LM134. Separating R
SET
from the LM134
requires 3 wires and has lead resistance problems, so is not
normally recommended. Metal film resistors with less than
20 ppm/˚C drift are readily available. Wire wound resistors
may also be used where best stability is required.
APPLICATION AS A ZERO TEMPERATURE
COEFFICENT CURRENT SOURCE
Adding a diode and a resistor to the standard LM134 con-
figuration can cancel the temperature-dependent character-
istic of the LM134. The circuit shown in Figure 3 balances
the positive tempco of the LM134 (about +0.23 mV/˚C) with
the negative tempco of a forward-biased silicon diode (about
−2.5 mV/˚C).
00569704
FIGURE 2. Gain Adjustment
LM134/LM234/LM334
www.national.com 6
Application Hints (Continued)
The set current (I
SET
) is the sum of I
1
and I
2
, each contrib-
uting approximately 50% of the set current, and I
BIAS
.I
BIAS
is
usually included in the I
1
term by increasing the V
R
value
used for calculations by 5.9%. (See CALCULATING R
SET
.)
The first step is to minimize the tempco of the circuit, using
the following equations. An example is given using a value of
+227µV/˚C as the tempco of the LM134 (which includes the
I
BIAS
component), and −2.5 mV/˚C as the tempco of the
diode (for best results, this value should be directly mea-
sured or obtained from the manufacturer of the diode).
With the R
1
to R
2
ratio determined, values for R
1
and R
2
should be determined to give the desired set current. The
formula for calculating the set current at T = 25˚C is shown
below, followed by an example that assumes the forward
voltage drop across the diode (V
D
) is 0.6V, the voltage
across R
1
is 67.7mV (64 mV + 5.9% to account for I
BIAS
),
and R
2
/R
1
= 10 (from the previous calculations).
This circuit will eliminate most of the LM134’s temperature
coefficient, and it does a good job even if the estimates of the
diode’s characteristics are not accurate (as the following
example will show). For lowest tempco with a specific diode
at the desired I
SET
, however, the circuit should be built and
tested over temperature. If the measured tempco of I
SET
is
positive, R
2
should be reduced. If the resulting tempco is
negative, R
2
should be increased. The recommended diode
for use in this circuit is the 1N457 because its tempco is
centered at 11 times the tempco of the LM134, allowing R
2
=
10 R
1
. You can also use this circuit to create a current source
with non-zero tempcos by setting the tempco component of
the tempco equation to the desired value instead of 0.
EXAMPLE: A 1mA, Zero-Tempco Current Source
First, solve for R
1
and R
2
:
The values of R
1
and R
2
can be changed to standard 1%
resistor values (R
1
= 133and R
2
= 1.33k) with less than
a 0.75% error.
00569728
FIGURE 3. Zero Tempco Current Source
LM134/LM234/LM334
www.national.com7
Application Hints (Continued)
If the forward voltage drop of the diode was 0.65V instead of
the estimate of 0.6V (an error of 8%), the actual set current
will be
an error of less than 5%.
If the estimate for the tempco of the diode’s forward voltage
drop was off, the tempco cancellation is still reasonably
effective. Assume the tempco of the diode is 2.6mV/˚C in-
stead of 2.5mV/˚C (an error of 4%). The tempco of the circuit
is now:
A 1mA LM134 current source with no temperature compen-
sation would have a set resistor of 68and a resulting
tempco of
So even if the diode’s tempco varies as much as ±4% from
its estimated value, the circuit still eliminates 98% of the
LM134’s inherent tempco.
Typical Applications
Ground Referred Fahrenheit Thermometer
00569715
*Select R3 = VREF/583µA. VREF may be any stable positive voltage 2V
Trim R3 to calibrate
Terminating Remote Sensor for Voltage Output
00569714
Low Output Impedance Thermometer
00569706
*Output impedance of the LM134 at the “R” pin is approximately
where R2is the equivalent external resistance connected from the Vpin
to ground. This negative resistance can be reduced by a factor of 5 or
more by inserting an equivalent resistor R3=(R
2/16) in series with the
output.
Low Output Impedance Thermometer
00569716
LM134/LM234/LM334
www.national.com 8
Typical Applications (Continued)
Higher Output Current
00569705
*Select R1 and C1 for optimum stability
Basic 2-Terminal Current Source
00569701
Micropower Bias Low Input Voltage Reference Driver
00569717
00569718
LM134/LM234/LM334
www.national.com9
Typical Applications (Continued)
Ramp Generator
00569719
1.2V Reference Operates on 10 µA and 2V
00569720
*Select ratio of R1 to R2 to obtain zero temperature drift
1.2V Regulator with 1.8V Minimum Input
00569707
*Select ratio of R1 to R2 for zero temperature drift
Zener Biasing
00569749
Alternate Trimming Technique
00569750
*For ±10% adjustment, select RSET10% high, and make R1 3R
SET
LM134/LM234/LM334
www.national.com 10
Typical Applications (Continued)
Buffer for Photoconductive Cell
00569751
Generating Negative Output Impedance
00569723
*ZOUT −16 R1 (R1/VIN must not exceed ISET)
In-Line Current Limiter
00569709
*Use minimum value required to ensure stability of protected device. This
minimizes inrush current to a direct short.
Schematic Diagram
FET Cascoding for Low Capacitance and/or Ultra High Output Impedance
00569721
*Select Q1 or Q2 to ensure at least 1V across the LM134. Vp(1
ISET/IDSS)1.2V. 00569722
FIGURE 4.
LM134/LM234/LM334
www.national.com11
Schematic Diagram (Continued)
00569711
LM134/LM234/LM334
www.national.com 12
Physical Dimensions inches (millimeters)
unless otherwise noted
Order Number LM134H, LM234H or LM334H
NS Package Number H03H
SO Package (M)
Order Number LM334M, LM334MX,
LM334SM or LM334SMX
NS Package Number M08A
LM134/LM234/LM334
www.national.com13
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
Order Number LM334Z, LM234Z-3 or LM234Z-6
NS Package Number Z03A
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves
the right at any time without notice to change said circuitry and specifications.
For the most current product information visit us at www.national.com.
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS
WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR
CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the body, or
(b) support or sustain life, and whose failure to perform when
properly used in accordance with instructions for use
provided in the labeling, can be reasonably expected to result
in a significant injury to the user.
2. A critical component is any component of a life support
device or system whose failure to perform can be reasonably
expected to cause the failure of the life support device or
system, or to affect its safety or effectiveness.
BANNED SUBSTANCE COMPLIANCE
National Semiconductor manufactures products and uses packing materials that meet the provisions of the Customer Products
Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain
no ‘‘Banned Substances’’ as defined in CSP-9-111S2.
National Semiconductor
Americas Customer
Support Center
Email: new.feedback@nsc.com
Tel: 1-800-272-9959
National Semiconductor
Europe Customer Support Center
Fax: +49 (0) 180-530 85 86
Email: europe.support@nsc.com
Deutsch Tel: +49 (0) 69 9508 6208
English Tel: +44 (0) 870 24 0 2171
Français Tel: +33 (0) 1 41 91 8790
National Semiconductor
Asia Pacific Customer
Support Center
Email: ap.support@nsc.com
National Semiconductor
Japan Customer Support Center
Fax: 81-3-5639-7507
Email: jpn.feedback@nsc.com
Tel: 81-3-5639-7560
www.national.com
LM134/LM234/LM334 3-Terminal Adjustable Current Sources
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements,
and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should
obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are
sold subject to TIs terms and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TIs standard
warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where
mandated by government requirements, testing of all parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and
applications using TI components. To minimize the risks associated with customer products and applications, customers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right,
or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information
published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a
warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual
property of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied
by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive
business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional
restrictions.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all
express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not
responsible or liable for any such statements.
TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably
be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing
such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products
and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be
provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in
such safety-critical applications.
TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are
specifically designated by TI as military-grade or "enhanced plastic."Only products designated by TI as military-grade meet military
specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at
the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use.
TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are
designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated
products in automotive applications, TI will not be responsible for any failure to meet such requirements.
Following are URLs where you can obtain information on other Texas Instruments products and application solutions:
Products Applications
Audio www.ti.com/audio Communications and Telecom www.ti.com/communications
Amplifiers amplifier.ti.com Computers and Peripherals www.ti.com/computers
Data Converters dataconverter.ti.com Consumer Electronics www.ti.com/consumer-apps
DLP®Products www.dlp.com Energy and Lighting www.ti.com/energy
DSP dsp.ti.com Industrial www.ti.com/industrial
Clocks and Timers www.ti.com/clocks Medical www.ti.com/medical
Interface interface.ti.com Security www.ti.com/security
Logic logic.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense
Power Mgmt power.ti.com Transportation and Automotive www.ti.com/automotive
Microcontrollers microcontroller.ti.com Video and Imaging www.ti.com/video
RFID www.ti-rfid.com
OMAP Mobile Processors www.ti.com/omap
Wireless Connectivity www.ti.com/wirelessconnectivity
TI E2E Community Home Page e2e.ti.com
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright ©2011, Texas Instruments Incorporated