Single supply op-amp query

[Colin Fraser]

I can't remember the part numbers right now, but Maplin in the UK sell a
couple of IC's that produce a low current -ve DC supply from a single rail
+ve DC supply, which is ideal for powering op-amps in applications like
these.
If you like I'll look up the number tonight...

Peace

Colin

On May 13,  3:48pm, johns at oei.com wrote:
> Subject: Single supply op-amp query
>
>      I have a theremin that gives a weak 2.5V max CV output that I need to
>      boost to around 10V max.  I would like to add a voltage amplifier to
>      scale the voltage to a usable level.  Unfortunately the theremin only
>      uses a single voltage power supply.  So in order to scale the CV
>      higher, I will need to use a some single supply op-amp.
>
>      I browsed over several National Semi data and application books and
>      could only find that they suggested using a LM3900 for single supply
>      operation.  The problem with the LM3900 when used as a positive
>      voltage (0V to <+V) amplifier with a single supply is that you can't
>      let the input go below .5V because you need to keep the input diodes
>      forward biased.  So you can see that a hefty portion of the CV range
>      will be wasted if my input range is only 0V-2.5V.  Basicly, the LM3900
>      in only linear on input voltages from .5V to <+V
>
>      Does anybody know of some available op-amp that can provide a
>      programmable gain with a single supply and input signal down to
>      ground?
>
>      John Speth - johns at oei.com
>-- End of excerpt from johns at oei.com



-- 
Regards,

Colin Fraser


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