[sdiy] NIC-waveshaper progress

[Grant Richter]

Hello Ian,

I am using a circuit you may find interesting.

Take the standard invert/non-invert circuit using 100K resistors and a JFET
switch from op-amp plus to ground.

Replace the JFET switch with a zener diode to ground. For positive voltages
the circuit will act as a voltage follower up to the zener voltage, then as
an inverter above the zener "fold" point. So with a 5 volt zener, a 0 to 10
volt sawtooth will be converted to a 0 to 5 volt triangle. Lower resistor
values give a sharper knee. A TL431 can make an adjustable fold point.

Low impedance output, single op-amp section.

I'm using the circuit as part of the "Joystick Axis Generator" to convert
the X and Y voltages to a "dome" function for a 2D equal power correction
curve.