The Universal Slope Generator is a unity gain voltage follower with voltage controllable slopes. The range of control is exponential, extremely wide, and the Rise and Fall times can be controlled independently. The range of the Slope Generator is sub-sonic to high audio frequency.

http://www.elby-designs.com/contents/en-us/p865_ES114_-_Universal_Slope_Generator.html

• ? mA +12V
• ? mA -12V
• ? mA 5V

Available as an assembled Module and as a DIY project.

No info about availability.