[sdiy] Faster LM358 replacement

Tom Wiltshire tom at electricdruid.net
Mon Feb 26 00:14:00 CET 2018


Could you change the filter design instead?

A MFB filter will give you better performance higher up in the stop band than a Sallen-Key for example. You might be able to design around the op-amp limitations.

Some discussion here:

http://www.ti.com/lit/an/slyt306/slyt306.pdf

The other big difference is that one is inverting and the other isn’t, but you might be able to fix that by flipping the DAC data upside down.

Tom

==================
       Electric Druid
Synth & Stompbox DIY
==================

> On 25 Feb 2018, at 21:30, sleepy_dog at gmx.de wrote:
> 
> Hey,
> 
> say, what opamp could I use as a faster replacement for the LM358?
> Should be able to work with GND as negative supply and get the output (almost) there like the LM358.
> Would be nice to have one that also can run up to +15V, but for my scenario at hand, 5V supply is enough.
> And it would be nice to know one that's also not very expensive. It's probably hard to beat lm358 price... but let's not exaggerate ;)
> 
> The application is an active filter to treat the DAC output for CV. Turns out the LM358 doesn't do such a good job there even at just a few kHz, i.e. the response curve starts to become less steep at the higher end quickly. (which even LTspice predicts, but I didn't bother to try the circuit with a LM358 model until now)
> 
> 
> - Steve
> 
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