Power supply for chips and chips in PI metal detectors

[alex---1967]

I recently learned about the existence of such devices - ADP7102/ADP7104.
ADP7102 is a CMOS linear stabilizer with low voltage drop.
Is it possible (is there any sense) to use such a device to power chips in metal detectors, in particular, the NE5534 chip in metal detectors such as SurfMaster PI or HammerHead PI?
Will there be any significant improvements?





https://www.micro-semiconductor.com/...CPZ-5.0-R7.pdf
The ADP7102 is a CMOS, low dropout linear regulator

FEATURES
Low noise: 15 μV rms for fixed output versions
Initial accuracy: ±0.8%

[alex---1967]

More

ADP7112 FEATURES Low noise: 11 μV rms independent of fixed output voltage

[alex---1967]

And what if we use the AD797 chip (low noise 0.9 nV/√Hz) instead of the traditional НЕ5534 (Input Noise Voltage . . . 3.5 nV/ Hz Typ). Will there be any improvements?

[Carl-NC]

It depends on the circuitry. Opamps have a power supply rejection ratio spec (PSRR) that should suppress supply noise. A typical number is 90dB which is a factor of 30,000, so 15uv of noise is reduced to 500pv. This is far below any thermal noise sources, say, in the preamp so I would not spend the extra money to get a pricey low noise LDO. In my designs I tend to use the AP2205 which is super-cheap and 30uv of noise, still well below what is really needed.

[Carl-NC]

And what if we use the AD797 chip (low noise 0.9 nV/√Hz) instead of the traditional НЕ5534 (Input Noise Voltage . . . 3.5 nV/ Hz Typ). Will there be any improvements?

Again, depends on the design. In a PI with a traditional 1k input clamp resistor, the AD797 won't help much.

[alex---1967]

Thank you, this is a good explanation.

[alex---1967]

Here is another question that has arisen.

Сarl wrote in the description of the Hammerhead project:
" ... it is desirable to have the cleanest supply voltage possible, so R20-C14 and R21-C15 provide low-pass noise filtering for both rails."

What is the original source of noise?

[dbanner]

Here is another question that has arisen.

Сarl wrote in the description of the Hammerhead project:
" ... it is desirable to have the cleanest supply voltage possible, so R20-C14 and R21-C15 provide low-pass noise filtering for both rails."

What is the original source of noise?

There are potentially many sources of noise. The power supply (specifically the 7660 chip) itself is being externally clocked. Regardless of whether internal or external clock, there is switching noise, also mains interference, any inductive loops which could potentially cause oscillations, RF, etc.
Hence the need for filtering using bypass/decoupling.

[Detectorist#1]

Hi Alex---1967,

It is recommended for users without much experience in hardware designs to not use "Low Drop Voltage Regulators". They have very specific requirements for the value, type and ESR (Equivalent Series Resistance) parameters of output capacitors for working stability.

[Detectorist#1]

More information for problem with stability of "Low Drop Voltage Regulators".