#110: Circuit Fun: Flexible Ramp Generator to create frequency sweeps using 555 timer and op amps

More circuit fun! Here is a flexible ramp generator circuit that uses a 555 timer and a couple of op amps. The ramp speed, magnitude and offset can all be freely adjusted. It was designed to be used with a function or signal generator that has a voltage controlled frequency input. By doing this, you can create a signal that sweeps linearly between one frequency and another. This is a very useful thing when testing many circuits including receivers, filters, amplifiers, etc. For those interested: the non-linearity at the start of the ramp is due to the dielectric absorption (soakage) that is prevalent in typical electrolytic capacitors (charge stored in the dielectric material). The effect is less pronounced in tantalum caps, and much better in ceramic and film caps. This is one reason why electrolytic caps are not recommended for critical or precise timing applications. A copy of the drawings from the video can be found here: http://www.qsl.net/w/w2aew//youtube/Flexible_ramp_generator_555.pdf