Need very sharp squarewave circuit

" Fast square wave generator -- bad ringing ... "

........ Phil

Fairchild Semiconductor's Tiny Logic Ultra High Speed (UHS) parts might do it for you

If you really want fast edge-speeds, have a look at Motorola's (On Semicondictor, FreeScale) ECLinPS parts, which are much faster, but only produce ECL-level voltage swings (0.8V). I've used ECL to drive long-tailed pairs of BFR92 (NPN) and BFT93 (PNP) wideband transistors to produce bigger voltage swings with (marginally) sub-nanosecond transition times, but you've got to put them on a carefully laid-out printed circuit board if you want to get that kid of performance.

Thanks to everybody who offered suggestions. What I finally did was to get a cheap old early-Pentium motherboard with a missing CPU, but a functional clock.

The "CLK" pin of the empty CPU socket had a pretty decent SQ wave at about 100 MHz, and the "Pci-CLK" pins of the PCI sockets had a fairly decent 40 MHz SQ wave.

john w.

Which "early-Pentium" still had a high-speed off-chip clock generator? Didn't Intel give that up after their 40MHz '386 with its 80MHz clock? I thought the Pentium clocks ran at the external bus speed, e.g. 50MHz for the original 75 - 100MHz Pentiums, and 66MHz for the 200MHz Pentium and 333MHz Pentium-II modules, etc.

You may be right. I don't actually know for sure that it was a Pentium. The guy who gave me the board said it had been a Pentium, but the only thing that I'm actually sure of is that it is a Socket-7 board. For my purposes, it didn't matter.

john w.