1
\$\begingroup\$

I need +15VDC and -15VDC dual supply for rail to rail supply of op-amp. I have found buck-boost inverters used for this task. I have a doubt whether the inductor in the buck-boost inverter circuit can affect or add noise to the amplifier circuit? I have found several circuits as follows

1. charge pump inverter 

2. voltage inverter 

3. buck-boost inverter 

4. positive and negative switching power supply

which one is most suitable for noise sensitive application?

examples module 1 module 2 module 3

\$\endgroup\$
  • 1
    \$\begingroup\$ The devil is in the detailed design and not in generalities. \$\endgroup\$ – Andy aka Jun 26 '19 at 11:07
  • 3
    \$\begingroup\$ All the supplies you list will add noise; the issue is what can your particular circuit accept. \$\endgroup\$ – Peter Smith Jun 26 '19 at 11:08
  • \$\begingroup\$ @Peter Smith my application is a thermocouple amplifier \$\endgroup\$ – qwerty Jun 26 '19 at 11:13
  • 1
    \$\begingroup\$ Stop being "general". Peter Smith asked what your particular circuit can accept. Stating that your application is a thermocouple amplifier is a generalism - as I said, the devil is in the detail. \$\endgroup\$ – Andy aka Jun 26 '19 at 11:16
  • 2
    \$\begingroup\$ What is meant is: there is no supply which delivers power with ZERO noise. Some supplies generate more noise and ripple than others. What is most important is to find out what your circuit needs. "The lowest noise" is not an answer. A proper answer is 1uV or 1 mV or 100 mV. You might be using a circuit which has an opamp with a very high PSRR, then you might be able to allow more noise and ripple on the supply. A thermocouple is a low-frequency measurement (nearly DC) so any noise in the amplified signal can be filtered out. \$\endgroup\$ – Bimpelrekkie Jun 26 '19 at 11:28
2
\$\begingroup\$

I like the cheapest solution US $2.88

But provide room to add a tin-plated brass or steel foil Faraday shield with an RC filter to desireable breakpoint near 10 Hz. There may be noise from this to the source may need shielding, isolation and filtering. How much? depends on your specs.

Also, when the output hits the rail, there is no PSRR. zero, 0dB nada, none

Module 1 specs at bottom of your link says 20 mA minimum load for best results.

    3W DC-DC Boost Converter 3.3V-12V to ± 15V Output Step up Power Supply Module.   
 
 Description:◦  Features:             


 ±15V step-up module, 3W positive and negative output boost module, low 3.3VDC input, non-isolated DC-DC

Power modules, Can replace LM78XX / 79XX three-terminal regulator chip.
  
 Wide voltage input: 3.3-13VDC
 Boost Dual output: ±15V
 Efficiency: 82%
 Size: 23.5 * 14 * 6.3mm


Support single in-line or horizontal installation DIP


Conversion efficiency: 5V input, full 3W output, 82%

  
     -  Ripple noise: **5V input, full 3W output, 60 ~ 120mV**.  
  
          - Port definition:       
           VIN: 3.3V to 13V DC input
    GND: Input Output Common GND
    +Vo: Output Positive.    
    -Vo: Output negative.  
    NC: Vacant port, no electrical connection
    En: Module enables:
    VEN < 0.8V, the module does not work;
    1.4V < VEN < VIN or EN vacant when the module normal output.
   NOTE: VEN < 0.8V, the circuit configuration restrictions, +Vo Vin voltage output at this time still, but -Vo no voltage output.


 Precautions

  1. The module does not support output short circuit protection board.
  2. The output current is greater than 20mA can get a better product overall performance.
  3. When -Vo overloaded, + Vo load is too light, it is recommended to increase the dummy load resistor between ground terminal and + Vo terminal.
\$\endgroup\$
  • \$\begingroup\$ I will be using AD8495 \$\endgroup\$ – qwerty Jun 27 '19 at 3:09
  • \$\begingroup\$ Add LPF to supply rails and 20mA dummy loads \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jun 27 '19 at 3:30

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.