LM334 easily sets a steady current even with changing loads. All that is needed to set the current is one external resistor connected from the R pin to the V- pin, and of course enough voltage to power everything.
Information not guaranteed to be accurate. Always consult the datasheet.
- Brief LM334 three terminal adjustable constant current source
- Brief charging capacitor voltage ramp circuit using LM334 current source
- Brief discharging capacitor voltage ramp using LM334 current source
Some rated values for the LM334:
- 1V – 40V
- 1µA – 10mA
- Set voltage of 64mV (0.064V) at 25°C (77°F)
- Pin layout (left to right, flat side facing you) 1, 2, 3 V+, R, V-
- Make sure to verify all information from me and others with the datasheet before using.
My LM334s seems to set the current based on 0.068V, which makes the math easier for me because I have resistors that start with 68 (6.8Ω, 68Ω, 680Ω), but none that start with 64. The different set voltage might be because I usually keep the temp around 70°F, as it does respond a bit to temperature.
LM334 3 terminal adjustable constant current source set with 1 resistor electronics demonstration
The current that the LM334 will let pass through it (and series components) is based on about 64mV (0.064V) divided by the set resistance. I have 6.8Ω and 68Ω resistors which pretty nicely passes 0.068V/6.8Ω = 0.01A (10mA) and 0.068V/68Ω = 0.001A (1mA)
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