Concerning the need for an anti-swamp resistor(s)

  • Thread starter Thread starter Scott McKie
  • Start date Start date
AI Thread Summary
Anti-swamp resistors, specifically .1R/5W, are essential in multi-parallel legged current booster circuits using an LM317 variable voltage regulator to ensure current balance among multiple supplies. Without these resistors, one supply may dominate, leading to overheating and potential failure due to increased current from temperature effects. In contrast, single parallel leg configurations do not require these resistors as the current distribution is more stable. The negative temperature coefficient of power BJTs necessitates these resistors to maintain similar currents and temperatures across the circuit. Proper implementation of anti-swamp resistors is crucial for reliable performance in these configurations.
Scott McKie
Messages
3
Reaction score
0
Why are .1R/5W resistors, known as "anti-swamp" resistors, required in a multi-parallel legged current booster schematic using an LM317 variable voltage regulator schematic when no resistor is shown on a single parallel legged current booster schematic using the same LM317? variable voltage regulator? This is not to be used in a audio amplifier configuration.
 
Engineering news on Phys.org
Scott McKie said:
Why are .1R/5W resistors, known as "anti-swamp" resistors, required in a multi-parallel legged current booster schematic using an LM317 variable voltage regulator schematic when no resistor is shown on a single parallel legged current booster schematic using the same LM317? variable voltage regulator? This is not to be used in a audio amplifier configuration.

Link to schematic...? :smile:
 
Hello Berkeman,
I am do not see any schematic (reference your reply) to link to. Can you please send me directions on where and how to do so.
Thanks,
Scott McKie
 
Scott McKie said:
Hello Berkeman,
I am do not see any schematic (reference your reply) to link to. Can you please send me directions on where and how to do so.
Thanks,
Scott McKie

Where did you see the circuit? Can you scan it and upload it? Or worst case, take a picture of it with your cellphone and upload the picture? I'm not familiar with the term "swamp resistor", so I'm not sure what to do a Google Images search for...
 
The resistors balance the current from the multiple supplies. If one supply provides more current then it may get hotter and the temperature coefficient may increase the current further, leading to failure. It will be swamped.

The VBE of power BJTs has a negative temperature coefficient. A series 0R1 is sufficient to keep the currents and temperatures similar.
 
  • Like
Likes berkeman
Thread 'How can I find the cleanout for my building drain?'

Thread 'How can I find the cleanout for my building drain?'

I am a long distance truck driver, but I recently completed a plumbing program with Stratford Career Institute. In the chapter of my textbook Repairing DWV Systems, the author says that if there is a clog in the building drain, one can clear out the clog by using a snake augur or maybe some other type of tool into the cleanout for the building drain. The author said that the cleanout for the building drain is usually near the stack. I live in a duplex townhouse. Just out of curiosity, I...
View full post »

Thread 'Query on Isentropic relationships (such as PV^gamma = constant)'

Hi all, I have a question. So from the derivation of the Isentropic process relationship PV^gamma = constant, there is a step dW = PdV, which can only be said for quasi-equilibrium (or reversible) processes. As such I believe PV^gamma = constant (and the family of equations) should not be applicable to just adiabatic processes? Ie, it should be applicable only for adiabatic + reversible = isentropic processes? However, I've seen couple of online notes/books, and...
View full post »

Similar threads

Electronics Designing a buck converter with feedback and a regulated output
Replies
4
Views
2K
Potentiometer alternatives
Replies
14
Views
7K
Controlling the power output of a power resistor
Replies
14
Views
2K
Can You Set Up 4 DC Motors in Parallel with a Variable Resistor and LED Strip?
Replies
11
Views
2K
Calculating Resistance in a Parallel Circuit without Voltage Information
Replies
8
Views
19K
Few smps and/or amplifier questions
Replies
2
Views
2K
Energy dissipated in the resistors in a 2 mesh RC circuit
Replies
1
Views
2K
Electrical How to use capacitors in a Solenoid circuit
Replies
32
Views
8K
Parallel resistance Rs in current source
Replies
1
Views
4K
Circuit with Resistors and a Battery
Replies
5
Views
13K

Hot Threads

Recent Insights

Back
Top