[sdiy] Single vs Dual Op Amp Supplies

[Matthew Smith]

Quoth Tom Wiltshire at 2009-03-08 20:10...
> The voltage offset. The best reason for using the dual-rail op-amps  
> is that you can get the signal moving either side of 0V and not have  
> any DC shift.

Understood.  Ah - so we're getting rid of DC so it's a pure AC signal, 
is that right?

> You need to add -2.5V DC to cancel the 2.5VDC shift that your  
> squarewave has. A simple inverting mixer will do, but since the mixer  
> inverts, you need to connect it to +2.5V instead.
Think I'm with you.  Will give this thought when not so tired and head 
not full of cold.

> David is right too; the integrator will produce an output amplitude  
> that halves for each octave increase in frequency. This has to be  
> compensated somehow. There's loads of "DCO" stuff on the web and in  
> the SDIY archive that offers one way, or otherwise you could use some  
> kind of variable gain circuit after the integrator.
The latter approach came to mind when Mr Brain finally woke up and I 
realised what David was talking about.  I'll try to work out possible 
solutions and THEN go Google on it.  Trying to use as much of my own 
thinking as possible, just getting advice on general principles.  This 
is my favourite learning method, or at least my most successful.

Thanks for that.  (Thanks David too - forgot to say in previous mails; 
brain right out to lunch.)

Cheers

M


-- 
Matthew Smith
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