Variable ramp generator

[Martin Czech]

:::Yeah, that should do. It's funny to observe somebody's favourite
:::solutions, BTW :-)
:::PWL diode ladder should be sufficiently precise in this application,
:::but I personally prefer to use one chip instead of several diodes.
:::
:::Tietze & Shenk (among many others) show, how to built a dividing
:::network by the use of a multiplicator (I think an OTA should do)
:::in a feedback of an inverting amplifier:
:::
:::        --------------
:::        |            |
:::        -     |\     |
:::Uz o-->|X|--->|-\    |
:::        -     |  \_--o---o Uy ~ Ux/Uz
:::              |  /
:::Ux o--------->|+/
:::              |/
:::
:::I am going to check this ASAP.
:::
:::thanks for all,
:::

In this case you should have an extra look at temperature effects.
I think such a cheap multiplier will be quite temperature
dependend.

m.c.