IC LM3900 Projects Book by Harry Kybett

bubzy

anyone know if there is a legitimate source i can download this from? its almost impossible to find a physical copy, and while i probably wont build anything from it because im too damned lazy, the mere fact that i cannot get this book, heightens my desire to do so!
cheers

JovianPyx · Posted: Sun Nov 13, 2016 10:22 am Post subject:

I can't help with that particular book, but I've seen lots of example circuits in the datasheets.

Just as a point of information, the LM3900 isn't a general purpose opamp. It is a special device designed for high noise environments like industrial systems. Unlike an opamp such as the TL series which is a voltage amplifier, the 3900 is a current amplifier - which is why it has good noise immunity. As such, it has rather low input impedance. This makes many synth applications difficult at best - which is why the 3900 is not popular among module and synth designers. You can probably order a few of the parts and satisfy your curiosity by breadboarding some of the example circuits.

http://www.ti.com/lit/ds/symlink/lm3900-n.pdf is a datasheet with the example circuits. Among them are filters (not voltage controlled), some oscillators, a sample and hold, phase locked loop and a voltage controlled (linear) current source. There are at least probably some lunetta-like applications that could be built around the 3900. Lots of example circuits - have a look.

You may also be able to see why the device has low input impedance by looking at the schematic of the internals of the device.

JovianPyx · Posted: Mon Nov 14, 2016 7:57 am Post subject:

What might be fun and interesting is to add FET voltage followers to the inputs of the LM3900. This would buffer the low impedance inputs and turn them into high input impedance inputs. That might make the LM3900 more acceptable for synth stuff. Of course, this makes it's use more expensive and physically messy...

AlanP · Posted: Mon Nov 14, 2016 10:06 pm Post subject:

If you want to study LM3900 in synth applications, Serge Tcherepnin never seems shy to use one. Ken Stone has a lot of old Serge schematics up.

wackelpeter · Posted: Tue Nov 15, 2016 8:18 am Post subject:

uniqview

I've been looking for this book forever as well. What annoys me is that I had a copy sometime in the 1980s, but lost track of it somehow. Cannot seem to find it now at antiquarian or other used bookstores either.

If you want to learn more about the LM3900, AN-72 still is very informative, and can be had from TI's website: AN-72.

The LM3900 is a very different, but interesting and versatile device. It is still available 48 years after it first shipped. It has esp. good qualities for single-supply systems: good bandwidth, fair open-loop gain, but only modest slew-rate. It is a tremendously stable device. I've personally been fascinated by the LM3900, and so I've been developing with it for SDIY applications. Among other things, I have found ways to use it more precisely, for instance. I have a blog about the device here: Beyond AN-72.

AlanP · Posted: Mon Jun 15, 2020 11:10 am Post subject:

Currently building a 208 Music Easel, and there are LM3900 chips dotted around it. I'm guessing the SNR is better than with the RC4136 opamps it also uses.