| bryman79 |
Hello All,
I currently have a Jung Regulator PCB made by AOS. Is it possible to modify it to output 5V without significantly altering the board? In the schematic (here: http://www.aoselectronics.com/gfx/jsr/jung_pos.gif), you can see that the reference voltage is 6.9V, so that clearly would have to be dropped below 5V for a 5V output. Any ideas?
Thanks,
Bryan |
|
|
| Elso Kwak |
| quote: | Originally posted by bryman79
Hello All,
I currently have a Jung Regulator PCB made by AOS. Is it possible to modify it to output 5V without significantly altering the board? In the schematic (here: http://www.aoselectronics.com/gfx/jsr/jung_pos.gif), you can see that the reference voltage is 6.9V, so that clearly would have to be dropped below 5V for a 5V output. Any ideas?
Thanks,
Bryan |
Other reference?
:cool: |
|
|
| bryman79 |
Any hints on a substitute reference that would equal the LM329 in performance? I see that some use the TL431... has anyone measured the noise at the output vs. the LM329?
Thanks,
Bryan |
|
|
| GaryB |
Bryan,
Try an LM385-2.5v. Its a good quality reference thats available in voltage ranges appropriate for a 5v regulator.
---Gary |
|
|
| bryman79 |
Gary,
Will substituting the LM385 require any other part changes (e.g., the 4.99k resistor)?
Thanks,
Bryan |
|
|
| bryman79 |
I've since run across ALW's pdf article that suggests using the LM336Z-2.5 and the AD817. I've emailed him, but no response. As such, I have two questions:
1. Why the change from AD825 to AD817? I've heard that both will operate at voltages below 5V...
2. Anyone have experience (listening or measuring) with the LM336Z-2.5 vs. the LM385-2.5?
Thanks,
Bryan |
|
|
| peranders |
I have tested with AD825 at 5 volts, even down to 3.1 volt and this is under the specs but it worked.
As reference a LM431 will work and surely many other references at 2.5 volts. |
|
|
| Elso Kwak |
You can use a 5V reference with a gain of 1 amplifier. In other words the regulator must have unity gain then.
LT1021-5, MAX6250, AD586, REF02. |
|
|
| peranders |
Dear Mr. Kwak, are you really sure?
The inputs will have the same potential as the output. You have common mode limits. I'll say 2-3 volts is better as reference voltage. |
|
|
| Elso Kwak |
It's working 3 years now Mr. Anders!
:rolleyes: |
|
|
| Elso Kwak |
A little schematic. On top the +5V regulator.
One reference for all.
Any questions?
:cool: |
|
|
| peranders |
| +- 20 V unstabilized voltage on OP07? A bit tough, don't you think? |
|
|
| Elso Kwak |
| quote: | Originally posted by peranders
+- 20 V unstabilized voltage on OP07? A bit tough, don't you think? |
Absolute maximum rating: +/-22V according to datasheet!
No failure in 3 years!
:cool:
:rolleyes:
:D |
|
|
| bryman79 |
Okay, so I got the regulator to output 5V. Thanks moamps for the link... I didn't realize the U3 diode needed to be changed. Since I didn't have a 2.2V-2.7V zener, I improvised with a green LED instead. Would I see improved performance by using another diode in this position? Any suggestions?
Thanks,
Bryan |
|
|
| peranders |
| Ideally the diode/zener make the output of the opamp to be at half of it's voltage swing and at least make sure that the output is under it's max value. A Led, any kind will do except for blue and white. 1.5-2 volts is needed. |
|
|
| moamps |
| quote: | Originally posted by bryman79
...I improvised with a green LED instead. Would I see improved performance by using another diode in this position? Any suggestions?
|
A green LED is just fine.
Regards,
Milan |
|
|
| bryman79 |
Deviating a bit from the thread title, but... can someone suggest a suitable reference and opamp for a 3.3V Jung?
I searched on DIYA, but came up with a bunch of false-positives... anyone have a link to a thread discussing this?
Thanks,
Bryan |
|
|
| peranders |
| I have actually tested AD825, way under it's specs but it worked with at least one unit. In this case it took the power for the opamp from the unregulated side (use preregulator) so it's regulated quite a bit in real life. |
|
|
|
