Re: Op Amp VCC+ to 30V using 5V source?

On Dec 16, 7:35 am, "DaveM" <masondg4...@xxxxxxxxxxxxx> wrote:
<jedd...@xxxxxxxxx> wrote in message

news:7bf30120-19c0-44d3-96ef-5b19d0142fe8@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx



NOW, the problem is that when I connect it to VCC+ and I connect the
VCC- of the op-amp to ground, the voltage at the input terminal goes
to 1V rather than the 30V when the circuit was not connected to
anything.

** Floating inputs can be anywhere from ground to Vcc.
Use the op-amp in a useful circuit.

I would appreciate any suggestions on how to get the +30V for the VCC+
for this amp... if there are modifications that I can make to the
circuit I have already built that would be great, but if not, any help
is GREATLY APPRECIATED!

** But you *ALREADY* stated you had a 30V supply, so you have no problem.

Thanks!

I do have a 30V supply, but apparently either 1) the output impedance
is too low, or 2) the current drive of my 30V source is not high
enough to act as VCC for the AMP.

When I said that the "input" goes to 1V, I actually meant that the VCC
when connected to the 30V source actually has the OUTPUT OF THE 30V
SOURCE GO TO 1V, so that would make the VCC just 1V, which is
completely useless to me...

How much current does your OPAMP circuit need? If it's more than 1 or 2 ma,
then your 30V power supply is not able to supply the current, thus the output
goes down. You need a better power supply.

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra
===========================================
Hello - I am new to this group so I hope this gets through
- I am unable to give a complete analysis because I do not know how
the LM324 is configured or if there are any mistakes.
- The 30 volt power supply circuit seems like it should drive an op
amp, but probably only as an instrument type of amplifier. There will
not be enough current to do any real work, like drive speakers etc...
- I would building the op amp part of the circuit with a known good 30
volt supply, get it working the way that you want and then measure all
currents and voltages.
- This should help determine what sort of power supply is needed for
the final design
- at the very least you can string together some 9 volt batteries for
testing purposes and this has the benefit of being a clean DC source.
- be advised that the ripple voltage goes up as current goes up when
using the` power supply as described.
signed Edward H. Bell
===================================================
.

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