| ??? 02/15/06 16:27 Read: times |
#110076 - Floating regulator Responding to: ???'s previous message |
Sursh said:
It is said that R7 is fixed and holds the voltage accross the o/p and adj terminal (1.24V). So by putting R7 = 120V/.25W will dissipate all power in it.
If this is the case, how could Q4 (emitter pin) receive voltage to drive the major part of the 10mA current through it. LM338 isn't a standard voltage regulator like LM7815 or similar. It does not produce a constant voltage at output referening to ground, but produces a constant voltage between output and adjust pin. This type of regulator is called 'floating regulator', because all it does is to produce a constant voltage between output pin and adjust pin, which can, shall and must float refering to ground. Correct output voltage is provided by letting the current (1.24V dropping across 120R resistor) running through an additional resistor, here Pot R6. Suresh said:
i would like to know how the diode nature helps to avoid this current flow. It shunts the current arround the regulator, at the same time limiting the voltage to one forward voltage drop of a diode. Suresh said:
How does a diode help in overcoming these problems. See above. Kai |
| Topic | Author | Date |
| 3A constant current source | 01/01/70 00:00 | |
| Where did you find it? | 01/01/70 00:00 | |
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| yes | 01/01/70 00:00 | |
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