Home > POWER > New Breed of Ultra Low Noise Regulators

New Breed of Ultra Low Noise Regulators

Update (6/30/14): Added TI LP5907, reviewed noise figures.

Update (2/1/14): Added the ADM7150/ADM7151 which is now at the top of the pack.

Update (01/29/13): Revised the noise density numbers

Update (8/27/12): Added the new TI TPS7A4700 regulator to the table. This device can source up to 1 A of current and ranks on top of the list. Also please ignore the noise density numbers, I need to revise them. Look at the RMS noise values.

The table below compares the noise level of some regulators used in current DIY modules vs a new breed of regulators that are used in portable consumer devices such as cell phones.

Just like phase noise in clocks, it is difficult to compare noise values among linear regulators because there is no common ground in specifying noise figures. Some companies report noise density, others RMS V noise, and yet others % of Vout. The frequency range for the reported noise figures also varies from company to company. Thus it is required to convert spec numbers to a common measuring unit. I chose to convert everything to “Noise Density” in nV/Sqrt(Hz) numbers. In order to understand the relationship between RMS noise and noise density, you can watch this video tutorial: http://www.youtube.com/watch?v=ywChrIRIXWQ [or here]

The noise density numbers are taken off the noise density spectra charts in the data sheets (D) or when not available from the datasheet they are calculated (C) in accordance to the relationship presented in the video above. They have been further normalized to a bandwidth of 100KHz. The number represents the “tail” of the noise spectrum which is typically a flat line.

The first two rows are application notes indicating the noise density value of the noise floor. AN51 is a discrete design using a ZETEX voltage reference. LM723 is an old part used in older designs. Newer monolithic designs have the added advantage that they are also very low dropout (LDO).

The comparison suggests that whether using a discrete design or state of the art monolithic regulators, we are very close to the measurable noise floor (~14 nV seems the best regulators so far…).

For the diyer, these devices are very small and maybe very hard to solder, especially the micro SMD bump package.

Regulator Used in Max Current
RMS Noise
Vout=3.3 (uV)
BW for noise spec Noise Density
nV/Sqrt(Hz) @100KHz
AN124 Noise floor 0.16 (peak) 0-10Hz 1? (not enough data)
AN83 Noise floor 0.5 10-100K 1.6(C)
ADM7150/7151 Discussion: [link] 800 1.6 10-100K 5.1(C), 1.7(D)
TPS7A4700 1000 4.0 10-100K 12(C), 12(D)
LP8900 200 6 10-100K 19(C), 25(D)
LP5907 diyinhk ES9018K2M 250 6.5 10-100K 21(C), 15(D)
LP5900 Lorien XMOS 150 6.5 10-100K 21(C), 12(D)
ADM7160 New Product (looks very similar to ADP151) 200 9 10-100K 24(D)
ADP151 Amanero USB, Ian’s FIFO 200 9 10-100K 28(C), 22(D)
AN51 350 3 10-22K 43
LM723 150 2.5 100-10K 79
LT1763, LT1761, LT1762 Buffalo II (LT 1763) 500 20 10-100K 63(C), 40(D)
TPS79333 Gamma-2 200 32 200-100K 101
LT1963, LT1964 Musiland power mod
1500, 3000 40 10-100K 126
LP2985 Opus DAC 150 30 300-50K 190
TPS786xx 1500 48 100-100K 152
LM340 1000 75 10-100K 237
LM317, LT1117 LCDPS, many low cost devices 1500, 800 99250 10-10K10-20K 3131 (?)3953 (?)

As previously discussed, the noise density numbers are an approximation assuming that it is “flat” throughout the bandwidth of interest. The area under the noise density trace is the RMS noise figure. So basically, if we assume a square area and a bandwidth of 100 KHz, then the RMS Noise = Noise Density X SQRT(100,000) = Noise Density X 316

Note: the second noise figure for the LM317 comes from TNT-Audio [link]. There, it is measured at 250 uV for the ~20Khz bandwidth.

Further reading: http://hifiduino.blogspot.com/2010/03/comparing-noise-figures-in-linear.html

  1. Florin
    March 30, 2011 at 16:49

    Very nice comparison, thank you! It is very interesting to notice the high performance of the 723 design, probably one of the oldest in this table, although is specified for 100Hz – 10 Khz.

  2. koas
    April 6, 2011 at 16:29

    koas :
    Hello, nice table.
    Perhaps rather than TPS79333 I would have put the TPS79101 family (15 uVRMS) from TI.
    There are also new regulators a litle more diy frendly (MSOP) as the TPS7A4901 with positive and negative version.

  3. Jochen.Lanz@de.de
    May 11, 2011 at 07:50

    Hey great overview solves alot of hassle like building own regs woithout dedicated tools and avoids the expensive regs (though they’re very good) from audiophile vendors!

    My only problem I can’t purchase the AN 124 ?? I can’t find it nowhere – did some one meanwhile??


  4. BlogGeanDo
    May 11, 2011 at 16:46

    AN124 is just an application note. I put it there as a reference point to show what is the minimum noise that can be reliably measured. The message being that ~ 1nV is the lower limit no matter what you do…

  5. Brian
    December 15, 2011 at 12:50

    It shoould be intresting to add also : LT1117 LT1764

  6. Anonymous
    January 25, 2013 at 17:14

    What about Micrel LDOs?

    • BlgGear
      January 25, 2013 at 18:08

      I am sure everyone is introducing new and lower noise LDO. The thing that “matters most” for audio is noise and current capability. We are now down to the single digit uV RMS noise in the 10 Hz to 100KHz frequency range. The other thing is transient response. Typically shown in a graph deep inside the data sheet.

  7. Bhupathy
    May 24, 2014 at 03:48

    I’m curious if anyone has experimented with using a 431 shunt with one of these low noise regulators. I see varying noise claims but 1-10Hz noise of a 431 seems lower than any of these series regs.

  8. TioFrancotirador
    July 7, 2015 at 21:19

    All those regs are good, but only for DVDD. I would never used them for AVDD. Here you need low noise of course, but also low impedance and flat frequency response. Any good quality shunt will better here. Among many I found Salas Reflector D the best.

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  1. May 9, 2011 at 01:17
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