-1

We have an instrument that has analog output of 0-1 volts and we need to convert this to 0-5 volts. What is the best op amp to use for this and how should the resistors be set up? Any help would be greatly appreciated.

Thanks,

Paul

  • For your frequency needs of course the 324 is the best, and the resistors should be setup for a gain of -5. – PlasmaHH Jun 15 '15 at 15:52
  • What have you tried? This is a very standard circuit; searching for "noninverting opamp" should turn it up. If you have specific trouble implementing it, that would be the time to ask for help with your more specific question. – Nick Johnson Jun 15 '15 at 16:10
  • Input impedance, output impedance, load impedance, frequency response, power supplies available? – Andy aka Jun 15 '15 at 17:44
  • 2
    Desired precision? Are we supposed to guess 10 bits because of the Arduino tag? – Spehro Pefhany Jun 15 '15 at 18:18
5

Since you used Arduino tag..., you don't need an opamp. Instead you can select ADC reference voltage on your arduino to 1.1V. This way you don't need any additional parts and you get the whole precision range.

analogReference(INTERNAL1V1);

http://www.arduino.cc/en/Reference/AnalogReference

  • +1 This is so neat, it's neat. Except if anything else needs the ADC - you are stuffed because the standard Arduinos (although there are so many these days..) only have a single ADC peripheral. Another thing is modular design - the analog instrument may not always be there or maybe needs other circuitry, so a simple general purpose rail-to-rail input/output op-amp with a gain of 5 and perhaps a passive low-pass filter going into the Arduino's ADC would be something I would do in my own design – KyranF Jun 18 '15 at 18:10
  • You can switch between 5V and 1.1V ADC in software as you like, so using mixing various peripherals is not a problem. – Cano64 Jun 18 '15 at 21:12
  • I suppose so, but no sure how much that would affect performance.. for a slow sensor-network system or whatever it would be fine - or just scale down all the other inputs to 1V using resistors which is far simpler than scaling a signal up. The resistors wouldn't be ideal if the signal itself was already a voltage divider as you would affect it with parallel resistance. – KyranF Jun 18 '15 at 22:39
  • @KyranF: Taken from the Atmega328 datasheet, Sect 24.5.2, paragraph 3: "the user may switch between AVCC [5 volts] and 1.1V [Internal Reference] as reference selection. The first ADC conversion result after switching reference voltage source may be inaccurate, and the user is advised to discard this result." – CharlieHanson Jun 22 '15 at 17:44
  • @chaaarlie2 thanks, thats pretty good only losing 1 sample – KyranF Jun 22 '15 at 20:05

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