oh, thank you very much, i reeeaaaally explains everything.
OK., seriously with EF there is no voltage gain from op-amp's output, so adjusting of output regulated voltage is only withing output swing of opamp. If one would need to adjust more, then they need to change the zener diode. Thread starter says something about 5-80V range... or have I misunderstood something??
Anyway supplying op-amp from output regulated voltage still may be problematic, first, zener voltage of ZD1 must be higher than minimum supply voltage for op-amp to make sure the whole stuff starts properly.
Second issue is the feedback. +V input to output. Hard to say anything sure about op-amp's open loop PSRR, for higher freqs may be very low or even nagative, than there is a threat of oscilation. I would add a resistor to the +V of an opamp together with the cap to form a RC filter as a frequency compensation. But it may be OK without it.
regards
Banned
Joined 2002
Translate from the designer:
1.
C9/C10/C19/C20 have nothing to do with oscillation
2.
The major components to adjust phase compensation are C3 & C13. Maybe RC compensation will do, but wouldn't be better.
This 2 caps are valued from 4.7PF ~ 47PF , depending on the OPamp used.
If you use certain high-speed OP, maybe you can not add this 2 caps.
3.
OPA637 can be stable when using on +-15V. AD825 is not reccomended.
4.
The reccomended OPAMP used on this Mini reg under 30V is OPA134. The sound is balanced.
If you use other OPAMP, may it will be better than OPA134 on HIFI aspect, but at the same time it will lose something.
Of course it is objective to every user.
You can try OPA627BP. Reccomended.
1.
C9/C10/C19/C20 have nothing to do with oscillation
2.
The major components to adjust phase compensation are C3 & C13. Maybe RC compensation will do, but wouldn't be better.
This 2 caps are valued from 4.7PF ~ 47PF , depending on the OPamp used.
If you use certain high-speed OP, maybe you can not add this 2 caps.
3.
OPA637 can be stable when using on +-15V. AD825 is not reccomended.
4.
The reccomended OPAMP used on this Mini reg under 30V is OPA134. The sound is balanced.
If you use other OPAMP, may it will be better than OPA134 on HIFI aspect, but at the same time it will lose something.
Of course it is objective to every user.
You can try OPA627BP. Reccomended.
1 I'm pretty sure that the regulator will oscillate with AD825 and C10, C20 but a slower opamp will be better in this sense. I'll guess there is a special reason why C10 and C20 not should be used.
3 Really? I think the Ad825 does an excellent job at least in my designs but OPA627 is not bad either.
4 OPA134 works fine, I'll agree but the design permits faster opamps which also generates less output impedance or at least the possibilities for it.
OPA627 isn't my first choice when price is involved.
I'll guess AD8610 is pretty good also but I haven't tested it yet.
3 Really? I think the Ad825 does an excellent job at least in my designs but OPA627 is not bad either.
4 OPA134 works fine, I'll agree but the design permits faster opamps which also generates less output impedance or at least the possibilities for it.
OPA627 isn't my first choice when price is involved.
I'll guess AD8610 is pretty good also but I haven't tested it yet.
Banned
Joined 2002
..
I have tested the single regulator and for test purposes I have taken almost the same parts as the original if you can call it that.
D44H11
BC560C
AD817 (hard to patch in AD825)
Gain 2 1k+1k
LM329
Voltage out = 14.1 V
I'll get oscillations even at 180 Ohms load (= 78 mA), around 4 MHz, 50 mV pp. I tested to do my trick with a small resistor in series with the opamp pin 7 and it gets even worse.
I have also tested more load and the oscillations get even worse, with a pure resistive load.
This test shows that the pcb isn't speedy enough if your goal is a fast regulator. Both ALW's and my layout can handle AD825 uncompecated without any problems and ALW's doesn't need a LP-filter to the opamp supply pin. ALW's pcb is impossible to get into oscillation (may have to do with internal inductance and true star ground. My regulator can be provoked if the load is low loss capacitive in parallel with a resistor and the cap wires are shorter than 20 mm (10 mm each pin).
Coffin, your friend's problem is I think that the ground currents are going close to the opamp. I think the grounding is the major problem. Using 350 V/us, 50 MHz requires a good pcb layout. In the parts list there are mentioned TL071, OPA134 and such and they may work perfectly although the regulator won't be "super" in the sence of being fast and with low output impedance (=much feedback, low gain))
D44H11
BC560C
AD817 (hard to patch in AD825)
Gain 2 1k+1k
LM329
Voltage out = 14.1 V
I'll get oscillations even at 180 Ohms load (= 78 mA), around 4 MHz, 50 mV pp. I tested to do my trick with a small resistor in series with the opamp pin 7 and it gets even worse.
I have also tested more load and the oscillations get even worse, with a pure resistive load.
This test shows that the pcb isn't speedy enough if your goal is a fast regulator. Both ALW's and my layout can handle AD825 uncompecated without any problems and ALW's doesn't need a LP-filter to the opamp supply pin. ALW's pcb is impossible to get into oscillation (may have to do with internal inductance and true star ground. My regulator can be provoked if the load is low loss capacitive in parallel with a resistor and the cap wires are shorter than 20 mm (10 mm each pin).
Coffin, your friend's problem is I think that the ground currents are going close to the opamp. I think the grounding is the major problem. Using 350 V/us, 50 MHz requires a good pcb layout. In the parts list there are mentioned TL071, OPA134 and such and they may work perfectly although the regulator won't be "super" in the sence of being fast and with low output impedance (=much feedback, low gain))
Hi P-A
Quote from designer:
1.please assemble MINI REG as partlist. You can do the listening test between MR as partlist and JSR to see its different.
2.Designer had already assembled and test Jung SR years ago. He suggest you remove C6 of JSR or C7 on ALW to see if there's any osc.
The cap will slow down the reaction of the regulator a lot, but you have to add 100uF to prevent oscilation.......
Who is faster?
3.Designer had LISTEN to MR and jung SR, So he knows the difference beteen this two reg.
4.PCB layout of Taiwan is well-known.
translate as above
cheers
Coffin
Quote from designer:
1.please assemble MINI REG as partlist. You can do the listening test between MR as partlist and JSR to see its different.
2.Designer had already assembled and test Jung SR years ago. He suggest you remove C6 of JSR or C7 on ALW to see if there's any osc.
The cap will slow down the reaction of the regulator a lot, but you have to add 100uF to prevent oscilation.......
Who is faster?
3.Designer had LISTEN to MR and jung SR, So he knows the difference beteen this two reg.
4.PCB layout of Taiwan is well-known.
translate as above
cheers
Coffin
My test was only the check the pcb "speed", not to test any possible quality, listening quality.
The only thing verified here is that an AD817 is too mighty for the pcb but ALW and mine will handle it perfectly.
If you use a 10 V/us amp and then change it to 350 V/us, this will often be not possible without problems. The difference is if the pcb is developed for 50-100 MHz bandwidths it will also work good with slower parts.
If you check out Walt Jung's splendid articles you'll see that he emphasize the importance of having ground currents flowing in certain places. Right now currents can flow freely over the MR board and IF you want to use a fast opamp, those currents must not go near the opamp or the reference. I have made divided groundplanes and ALW has made a starground. Which is the very best I don't know. Starground has advantages but so does also a smart groundplane.
Since I'm not alone here with these pcb's I'm sure a couple of the rest will build regulators according to the partslist and then also verify the output, both with low currents and high and with capacitive load with short and long wires.
The only thing verified here is that an AD817 is too mighty for the pcb but ALW and mine will handle it perfectly.
If you use a 10 V/us amp and then change it to 350 V/us, this will often be not possible without problems. The difference is if the pcb is developed for 50-100 MHz bandwidths it will also work good with slower parts.
If you check out Walt Jung's splendid articles you'll see that he emphasize the importance of having ground currents flowing in certain places. Right now currents can flow freely over the MR board and IF you want to use a fast opamp, those currents must not go near the opamp or the reference. I have made divided groundplanes and ALW has made a starground. Which is the very best I don't know. Starground has advantages but so does also a smart groundplane.
Since I'm not alone here with these pcb's I'm sure a couple of the rest will build regulators according to the partslist and then also verify the output, both with low currents and high and with capacitive load with short and long wires.
I think I must make myself clearer in this.coffin said:
1 There is no such thing as a "perfect" pcb or pcb layout. You can always improve it.
2 You have most of the time trade-offs which results in a not perfect pcb.
3 Sometimes or even often "good" is suffiicient in performance, best possible is maybe not necessary
4 What is "good" really?
As you see you have a complex picture and it's not black or white, rather different colours.
If we talk mechanical quality the pcb's are excellent.
The have a "nice look and feel" and the purple colour is nice.
Hi,
Quoting from designer:
1.The sample of mini reg will be provided continously. Each member can apply for 2 PCB sample: one dual and one positive. Not selling any.
Please assemble the REG as the partlist suggest.
2.The purpose of regulator is to provide same frequency response at audio range. and must be stable at high frequency range to avoid intermodulation.
Just like the preamp or poweramp, you will not paralell a 100uF cap at the feedback resistor to prevent the instability as well as cut the signal above 1Hz.
The response speed to all audio frequency is very crucial to regulator. DC voltage supply doesn't mean the circuit only needs 0Hz.
3.Again, the layout ability of Taiwan is EXCELLENT. Mainboard of the computer you are using is most come from TWN.
interprete as above
cheers
Coffin
Quoting from designer:
1.The sample of mini reg will be provided continously. Each member can apply for 2 PCB sample: one dual and one positive. Not selling any.
Please assemble the REG as the partlist suggest.
2.The purpose of regulator is to provide same frequency response at audio range. and must be stable at high frequency range to avoid intermodulation.
Just like the preamp or poweramp, you will not paralell a 100uF cap at the feedback resistor to prevent the instability as well as cut the signal above 1Hz.
The response speed to all audio frequency is very crucial to regulator. DC voltage supply doesn't mean the circuit only needs 0Hz.
3.Again, the layout ability of Taiwan is EXCELLENT. Mainboard of the computer you are using is most come from TWN.
interprete as above
cheers
Coffin
Banned
Joined 2002
If we exclude that 1 A diodes are used and the width of the traces, max current is determined by how much current the current generator is set to and how much current gain the output transistor has. The design is pretty general but you must beware of that higher output current will decrease the output impedance and therefore it will be more sensitive against capacitive load. One way to increase the current is to use a mosfet like in the Invisus Super Regulator.
Just wondering, what are the reasons for the Q2 forming a current mirror?
As I see it the absolute value of the current isn't particulary important but the drawback is that you'll loose 0.7 volts in dropout voltage which can be valuable sometimes.
What does the desinger say about this?
It's a shame that he can't any english. It would maybe have been easier to discuss more directly.
As I see it the absolute value of the current isn't particulary important but the drawback is that you'll loose 0.7 volts in dropout voltage which can be valuable sometimes.
What does the desinger say about this?
It's a shame that he can't any english. It would maybe have been easier to discuss more directly.
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