Pseudorandom Noise Generators

[PRR]

> 741 opamps made in the 1970s, they will be as noisy as you're likely to get an opamp being.

I used a lot of '741 class chips. They are not wildly more hissy than TL072. Vintage chips are likely to have "excess" noise, not consistent one to the next and maybe not the same device minute to minute. TL072 have more gain than a single '741, and most will be consistent (Silicon physics and gain-spec) except maybe 1/f corner.

Between analog and digital-- that becomes a religious preference. Someone who worships at the digital altar may find analog design daunting. Someone with OCD can never forget there is a digital chip amongst the analog sheep.

[anotherjim]

Good work RG. I never meant to rubbish a coded solution, hope it didn't come over that way. A cheap programmable part ought to be a go-to solution for everyone. The fact that it isn't is probably outside the scope of this thread.

That said, specifying old parts to get something new made isn't really tenable except in an "I need this now and these old bits lying around will have to do" emergency. So even though I know where to get some CD4006, I've never bought any and don't plan to.

[R.G.]

I didn't take it that way A.J.  No worries.   

@PRR: I must have had some bad ones, then. I quit using 741s early on for a number of reasons, noise being one of them. Of course, at the time in my life, I was poor enough that I used surplus semiconductors for all of my home tinkering. That probably biased my thinking.