參數(shù)資料
型號(hào)： LM234D
廠商： 意法半導(dǎo)體
英文描述： THREE TERMINAL ADJUSTABLE CURRENT SOURCES
中文描述： 三端可調(diào)電流源
文件頁(yè)數(shù)： 7/14頁(yè)
文件大?。?/td> 273K
代理商： LM234D
Application Hints
(Continued)
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 ex-
ample will show). For lowest tempco with a specific diode at
the desired I
, however, the circuit should be built and
tested over temperature. If the measured tempco of I
is
positive, R
2
should be reduced. If the resulting tempco is
negative, R
should be increased. The recommended diode
for use in this circuit is the 1N457 because its tempco is cen-
tered at 11 times the tempco of the LM134, allowing R
= 10
R
. 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% re-
sistor values (R
1
= 133
and R
2
= 1.33k
) with less than a
0.75% error.
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 ef-
fective. Assume the tempco of the diode is 2.6mV/C instead
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 68
and 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
DS005697-15
*
Select R3 = V
REF
/583μA. V
REF
may be any stable positive voltage
≥
2V
Trim R3 to calibrate
L
www.national.com
7
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LM234DT 功能描述:板上安裝溫度傳感器 3-Term Adjust Currnt RoHS:否 制造商:Omron Electronics 輸出類(lèi)型:Digital 配置: 準(zhǔn)確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor
LM234DT-CUT TAPE 制造商:ST 功能描述:LM234 Series 40 V 10 mA Three Terminal Adjustable Current Sources - SOIC-8
LM234H 制造商:nat'l 功能描述:
LM234H6 制造商:Linear Technology 功能描述:Constant Current Source and Temperature Sensor 3-Pin TO-46
LM234H-6 制造商:Linear Technology 功能描述:Constant Current Source and Temperature Sensor 3-Pin TO-46
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