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+5VDC & -15VDC FROM +15VDC SUPPLY QUESTION

DAVE Wallace
Prodigy 140 points
Other Parts Discussed in Thread: LM675, LM3886

+5VDC & -15VDC FROM +15VDC SUPPLY QUESTION

REASON I ASK IS I DON'T KNOW 100% FOR SURE? ANY ENGINEER'S ANSWER.

FROM +15VDC I WANT TO POWER an AD570, DATASHEET SUGGESTS USING +5V AND -15V SUPPLY.

CAN I DO THIS WITH 'CONDOR B15-1.5' (OUTPUT 15VDC@1.5 AMPS) D.C. POWER SUPPLY'S OUTPUT CONNECTED TO 3 ELEMENT SERIES RESISTOR “VOLTAGE DIVIDER” Et=15=E1+E2+E3 15=5+5+5 (USING 10K OHM ELEMENTS)

OK, Et=E1+E2+E3 GIVEN THAT, HOW DO I “SPLIT” THE SUPPLY, HOW DO I GET NEGATIVE VOLTS OR POTENTIAL DIFFERENCE; DO I REVERSE THE POLARITY? DO I INVERT THE Vs CONNECTIONS, DO I TREAT 0VDC, THE POWER SUPPLY GROUND I GUESS, AS -15VDC?

0VDC AND -15VDC, HOW DO I GET THAT? CAN I GET THAT FROM PRIMARY CELLS IN SERIES IN BATTERY HOLDERS? DRAW ME A SCHEMATIC?

I JUST NEED A SIMPLE ANSWER.

I CAN SUPPLEMENT THIS TEXT WITH A PLETHORA PICTURES TAKEN BY A CELL PHONE CAMERA, BUT I DONT LIKE USING MY TIME LIKE THAT FOR A SIMPLE QUESTION LIKE THIS, THAT WOULD BE FUNNY.

I TRIED MY HAVING MY PARTS SUPPLIER TECHNICAL SUPPORT ANSWER THIS OVER THE PHONE.

“IS 100nF=.01uF?”

'YES.'

“BINGO.”

DATASHEET REFERENCE https://www.i-components.nl/pdf/ce-AD570SD.pdf (AD570.pdf)

  • 0
    Prodigy 140 points

    JUST NOTICED

    I NOTICED LM675 HAS A DATASHEET W/ SCHEMATIC FOR GENERATING SPLIT SUPPLY FROM SINGLE SUPPLY, YES.

    CAN I SUBSTITUTE LM3886 FOR LM675, WHY NOT THEY'RE BOTH OP-AMPS.

    CAN LM3886 USE SCHEMATICS FEATURED IN LM675 DATASHEET?

    I ORDERED TWO LM3886'S SEVERAL YEARS AGO FROM TWO DIFFERENT SUPPLIERS, BOTH FAILED, USING TYPICAL APPLICATION SCHEMATIC IN DATASHEET.

    I WOULD LIKE TO DO SOME ADDITONAL TESTING TO CONFIRM.

    COUPLE QUESTIONS: CAN BI-POLAR IC'S LIKE THE LM3886 SUFFER ESD FROM BEING STOWED IN A BOX AND MOVED, MAYBE HANDLED WITHOUT ESD PROTECTION? MY ANSWER IS NO, BUT I COULD BE WRONG.

    IN THAT CASE, THERE'S NO ESD DAMAGE, SO EITHER THE TYP. APP. SCHEMATIC WAS WIRED INCORRECTLY, TOO MUCH HEAT WHEN SOLDERING, OR THE IC IS DEFECTIVE.

    IF THE LM3886'S ARE DEFECTIVE, WHAT IS TI'S POLICY ON DEFECTIVE SEMI'S?

    ONE WAS ORDERED FROM DIGIKEY, LM3886TF AND ONE WAS ORDERED FROM MCM-ELECTRONICS(NOW NEWARK) LM3886 BOTH IN APRIL 2017.

    WAS THOSE SEMI'S A BAD BATCH RUN FROM NATIONAL, AND WERE SOME OF THE SEMI'S AFFECTED FROM NSC?

    THANK YOU FOR YOUR ATTENTION.

    REGARDS

    DAVE

    “CAN I SUBSTITUTE LM3886 FOR LM675?”

    'WHY NOT THEY'RE BOTH OP-AMPS.'

    “& BINGO WAS THE PART NUMBER?”

  • 0
    Guru 316690 points

    You cannot use a voltage divider directly as a power supply, because any load will change the divider's output voltage. (You could use a voltage divider to generate a reference voltage for an opamp, but using an actual voltage reference chip would make you independent from fluctuations of the original power supply.)

    The +5V and -15V voltages are measured relative to the common ground, so you need a power supply that can generate two rails that are 20 V apart. Your 15 V supply is not capable of doing this. (And the AD570 draws a few milliamperes. Using a 1500 mA supply would be overkill.)