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How to remove small square wave/pulse from the output of LM317?

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ichibindigi

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Hello

Im having problems using the LM317 current limiter configuration. Im tryin to input a squarewave (fig a) and im assuming that a squarewave (fig b) should be the output having the same amplitude and frequency, provided that i don't exceed the current limit that Ive set for the LM317 circuit. The problem is that the output always becomes fig c it still has the same frequency and amplitude but a small squarewave/pulse always appear on its off cycle on the output. What should i do to have this small squarewave/pulse removed. Thanks in advance

ichibindigi

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oddbudman

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lm317 oscillation

Is there a reason for the JPG having an IC called a LM117 not a LM317?

What is the load you are driving?

What are the voltages on the waves?

What frequency are you running it at?

Can you use a 2 channel CRO and see if there is any delay between IN and Out?
 

paulux

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lm317 testing

I guess LM317 could not be used in this way. It seems to me that internal oscillation happens in your case.
 

ichibindigi

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back view of lm317

Is there a reason for the JPG having an IC called a LM117 not a LM317?

What is the load you are driving?

What are the voltages on the waves?

What frequency are you running it at?

Can you use a 2 channel CRO and see if there is any delay between IN and Out?

LM317/LM117 they basically the same thing
no load
10Vp-p
40Mhz

what is 2 channel CRO?

I guess LM317 could not be used in this way. It seems to me that internal oscillation happens in your case.

Ive tried to input a sawtooth waveform basically having the same frequency and amplitude the output was fine works fine without unwanted oscillation at all.
 

IanP

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lm317 current limit

Testing "current limitter" without load doesn't make much sense ..
Try to connect a load that will force the LM317 to act .. and test again ..

2-channel CRO = 2-channel Cathode-Ray Oscilloscope (CRO).

Regards,
IanP
 

Davood Amerion

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oscillating lm317

i have problem to download your figure! but i think LM317 can not pass 40MHz!
 

sabu

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lm317 test

i tnk it is due to the capacitor sitting at the out put.that may discharge when out put is low.this will not happense if u r giving saw tooth as input.plz check it out.
regards sabu
 

ichibindigi

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lm317 ripple frequency

Testing "current limitter" without load doesn't make much sense ..
Try to connect a load that will force the LM317 to act .. and test again ..

2-channel CRO = 2-channel Cathode-Ray Oscilloscope (CRO).

Regards,
IanP

It improve a little bit the ripples were lessen. Got any suggestion or an alternative circuit. that would do the trick
 

darKnight110588

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Re: LM317 Question

i used lm317 as to create a 3.3V output... but instead of having 3.3V output it created a more or less 1.2V output. I'm pretty sure that i used the right value for r1(240ohms) and r2(400ohms). my input voltage is 12V. I tried to change the value of the resistor, still the output is 1..2V. what might be the problem?
 

Audioguru

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LM317 Question

You probably have the ADJ and the Out pins backwards. Look at the pins on its datasheet.

You are also using resistor values for the more expensive LM117 instead of the 120 ohms and 200 ohms for the LM317. Again look at the datasheet.
 

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