The nerds' corner

[jubal81]

So I often find myself just sitting at the computer surfing EE sites, data sheets, etc. and thought it would be cool to have a thread to share good tidbits of lernin'.

Here's a paper on what to do with unused opamps in a design.

The idea is to avoid wasted power, stress and noise, you should make sure it has a reference voltage and give it feedback. So something like this:

[jtn191]

Like the idea of this thread. Isn't this already one of the nerdier corners of the internet? 

I'd like to share these transistor charts:
http://www.beavisaudio.com/techpages/Transistor-Pinouts/index.htm

not only does it help with pinouts, it gives hfe/gain ranges
-tip on what I've learned: don't underestimate low gain transistors, especially in fuzzes and wahs. Vintage transistors were low gain. Modern transistors are high gain. Try low gain transistors where you're going for a "vintage" sound

[stecykmi]

Like the idea of this thread. Isn't this already one of the nerdier corners of the internet? 

well at least we've got the musician-thing going for us, haha.

i thought i'd share these design notes on active filters. published by texas instruments. very mathy but lots of good info, especially on the different filter implementations.

[DutchMF]

Like the idea of this thread. Isn't this already one of the nerdier corners of the internet? 

Hell no! What we do here is usable in the real world on a day-to-day basis! For a really small portion of the worlds population, but still usable.....  I really like this thread-idea, hope to contribute something soon!

Paul

[culturejam]

The idea is to avoid wasted power, stress and noise, you should make sure it has a reference voltage and give it feedback. So something like this:

Diagram A is what we'd be doing most of the time.

But you might as well use that output as VREF for the rest of the circuit, instead of just tying it off. Buffered VREF is more stable and can be less noisy in some applications.

In the Box of Hall and Tenebrion reverb circuits, that's exactly what I did. Only needed three op amps for the audio, so I used the leftover amp to buffer VREF.

[jubal81]

The idea is to avoid wasted power, stress and noise, you should make sure it has a reference voltage and give it feedback. So something like this:

Diagram A is what we'd be doing most of the time.

But you might as well use that output as VREF for the rest of the circuit, instead of just tying it off. Buffered VREF is more stable and can be less noisy in some applications.

In the Box of Hall and Tenebrion reverb circuits, that's exactly what I did. Only needed three op amps for the audio, so I used the leftover amp to buffer VREF.

That's definitely some good thinkin'. I'd noticed that when I saw your schematic because I do love my reference buffered.

[jubal81]

Came across a fun toy at Analog devices. 
This web app designs filters to your specification.

You choose the filter type, components, etc. and it shows you the circuit. Neat stuff!

[RobA]

...
i thought i'd share these design notes on active filters. published by texas instruments. very mathy but lots of good info, especially on the different filter implementations.

That's a great reference. I used it to learn how filters worked back when I was only doing digital stuff just so I could get a better understanding. In general, TI's got a ton of really good application notes. I posted a link to this one on op amps in another thread, but it is worth sharing here too,
http://www.ti.com/lit/an/slod006b/slod006b.pdf.

If you are into the history of this stuff, TI has this great paper on op amps which has to be one of the earliest papers on op amps. It's written by Thomas Brown, the Brown in Burr-Brown.
http://www.ti.com/lit/an/sboa092a/sboa092a.pdf

[midwayfair]

Came across a fun toy at Analog devices. 
This web app designs filters to your specification.

Awesome. It's like a top-down version of this:
http://sim.okawa-denshi.jp/en/CRhikeisan.htm

[RobA]

Came across a fun toy at Analog devices. 
This web app designs filters to your specification.

Awesome. It's like a top-down version of this:
http://sim.okawa-denshi.jp/en/CRhikeisan.htm

These are both really useful. I've bookmarked them both. Thanks!

[jubal81]

Just picked up this interesting nugget on opamp noise and design:

"The amplifier's own voltage noise is always amplified in the non-inverting mode; thus when an op-amp is used as an inverting amplifier at a gain of G, its voltage noise will be amplified by the noise gain of (G+ 1). For the precision attenuation cases, where G<1, this may present problems. (A common example of this is an active filter circuit where stopband gain may be very small but stop-band noise gain is at least unity.)

Only the amplifier voltage noise-and any noise developed by the noninverting-input current noise flowing in any impedance present in that input (for example, a bias-current compensation resistor)-is amplified by the noise gain."

[jubal81]

This is breadboarding like a sir. Tons of great tips.

[gtr2]

Nice!  I thought I was a half decent breadboarder until I watched this 

Gotta give some of those tricks a whirl.

Thanks for sharing!

Josh

[midwayfair]

This is breadboarding like a sir. Tons of great tips.

This makes me feel inadequate. :p

[jkokura]

Yeah... I thought I was pretty good at it too.

Now I know I'm not.

Jacob