New project: Sequencer

[jhaible]

> It's trick from National app. note AN-4 (well,with matched fets but
> noted that CMR is not good because of them and resistors as current
> sources).

Haven't see AN-4, but I do know about the use of matched FETs for
this purpose. Problem is that dual FETs are very expensive. So
I was impressed by the use of a cheap 4007 chip.

> Back then it was problem in technology to produce quality FETs and 
> matched p and n channel MOSFETs on the same chip layer with opamp.
> Before early '70ies it was even problem to make such things as 4007
> as remaining Na in layers caused treshold/pinch voltage of n and p 
> mosfets to move in oposite directions which was bad for using in 
> logic gates.Sometimes it became depletion instead enhacement mode 
> mosfet during diffusion.

Interesting !

JH.