Volage Controlled Glide
    This is a voltage controlled glide.  This was done around 1980.  One feature of this circuit is that with the diode bias current set the way it is, you will bet a more or less linear ramp with rounded corners.  If the diode bias is removed, you will get a very linear ramp.  If you were to increase the diode current, you will get an exponential response.  It should be noted that for best performance, there should probably be a unity gain buffer on the input.  The bais current flowing out of the input is pretty high and will cause inaccuracies if the source has any appreciable output impeadence.