Charles:

I am glad to hear that the reference information will be useful to you. I was kind of wondering where Google took you when you searched and did not turn up any information.

I am surprised that you have to punt with "the simple inverter crystal circuits work as intended".
I would suggest to you that they appear to work as intended when in reality the type of dual inverter oscillator made with inverters with 500 ohm feedback resistors hammers the dickens out of poor crystals. Particulary those old fashioned digital nightmares made with 7404's, 74S04's or 74LS04's. Another thing to keep in mind is that as process technology has gotton better and better the crystals are being made smaller than ever before. A quick look in a DigiKey catalog or at a crystal manufacturers web site will show some of the amazingly small surface mounted crystal packages that are now available. Some (if not many) of these smaller parts must be carefully dealt with since the safe drive levels are lower than those of crystals 15 years ago in HC-49/U type cases.

If one needs to stay away from the transistor type of oscillator then look at the reference material where a very effective oscillator can be built with the unbuffered version of a CMOS inverter. These circuits also show a resistor in series with the crystal that keeps the drive level to the crystal to a level that is safe for the crystal.

I also tend to have respect for microprocessor and microcontroller manufacturers that have designed their on-chip crystal oscillators in a way that there is a drive limiting resistor used in series with the crystal. One such vendor is Motorola. Look at Figure 7-2 on page 119 of this document.

All in all I think it best to try to understand the problems with overdriving crystals in oscillator circuits and adapt design techniques that lead to better products. Off handed acceptance of dual 7404 circuits with low impedance feedback resistors that came into being more than 25 years ago seems to not be in best interest of anyone anymore.

Michael Karas