Re: How do I convert 0-10V to -5V +5V differential?

On 1 Sep 2005 08:01:11 -0700, "Chris" <cfoley1064@xxxxxxxxx> wrote:

>
>John Fields wrote:
>> On 31 Aug 2005 13:13:19 -0700, kasterborus@xxxxxxxxx wrote:
>>
>> >Thanks for you all your help - I have all the parts to build the op-amp
>> >solution at home - the only thing that puzzles me a bit is the
>> >+15V/-15V power to the 741 - how do I create +15 and -15V from a
>> >standard transformer.
>>
>> ---
>> Since the 741 can take an input supply of plus and minus 22 volts,
>> max, you can easily get less than that that from a simple,
>> unregulated, half wave supply using a 12V transformer, like this:
>>
>>
>>
>> +--[IN4001>]----------+---->+17V
>> | |
>> | |
>> MAINS>--+ || +--[<1N4001]--+-------|---->-17V
>> | || | | |
>> P || S | |+
>> R || E [C1] [C2]
>> I || C |+ |
>> | || | | |
>> MAINS>--+ || +-------------+-------+---->GND
>>
>>
>>
>> Since your output is only going to swing between +5 and -5V, and the
>> 741 needs about 3V above and below that to let that happen, you've
>> got about 9V of headroom to either rail so C1 and C2 can be fairly
>> modest, depending on what else you're going to use the supply for.
>>
>> What can you tell us about the load?
>>
>> --
>> John Fields
>> Professional Circuit Designer
>
>Mr. Fields has given the best solution. The OP might want to add a
>couple of protection diodes to keep the inputs in the range of the
>supplies and the caps from being reverse-biased at turn-on, like this
>(view in fixed font or M$ Notepad):
>
>` D
>` o------o-------->|----o-----o------o+14VDC
>` | +| |
>` | C --- - D
>` o------|---. --- ^
>` | | | |
>` 10.2VAC | '----------o-----o------o
>` from | +| |
>` Wall Wart | C --- - D
>` | --- ^
>` | D | |
>` '--------|<----o-----o------o-14VDC


---
Since we have current being steered into either one cap or the other
by the main rectifying diodes, I don't see how either of them could
become reverse-biased, since there's no available path.

Likewise, I don't understand what you mean by "to keep the inputs in
the range of the supplies."





--
John Fields
Professional Circuit Designer
.

Relevant Pages

  • Re: How do I convert 0-10V to -5V +5V differential?
    ... John Fields wrote: ... >>standard transformer. ... supplies and the caps from being reverse-biased at turn-on, ... Nearly all of the ones I'm familiar with have the dual supplies ...
    (sci.electronics.basics)
  • Re: Substituting electrolytic capacitor.
    ... John Fields wrote: ... I can't seem to find any .2 caps. ... isn't a standard value (except from some ancient US suppliers). ...
    (sci.electronics.basics)
  • Re: +/- 5 vdc signal to 0-10 vdc signal
    ... John Fields wrote: ... supplies then something like this is along the same lines: ... View in a fixed-width font such as Courier. ...
    (sci.electronics.design)