Rainbow Electronics LM334 - Manual (Page 8)

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 68
Ω 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
00569715
*Select R3 = V REF /583µA. V REF 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 R
2
is the equivalent external resistance connected from the V − pin
to ground. This negative resistance can be reduced by a factor of 5 or
more by inserting an equivalent resistor R
3
= (R
2
/16) in series with the
output.
Low Output Impedance Thermometer
00569716
LM134/LM234/LM334
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