Jim Thompson wrote:
Circuit Challenge of the Day

The following circuit...

http://analog-innovations.com/SED/Ra..._Amusement.pdf

is a ramp generator.

It is easy to see how the upper trip point circuitry causes discharge
of the ramp.

But what causes the turn-around at the bottom?

...Jim Thompson
As the collector current of Q1 drops to zero, its VBEsat drops below the
level needed to keep Q4 turned on, due to that 200 ohm resistor dropping
100 mV.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net