Dear Dennis... analogZONE's Dennis Feucht answers your design queries in his new Circuit Design Clinic! May 2007

analogZONE presents an interactive analog design service to readers! Send us your design questions (with relevant data; schematics in JPEG or GIF, please) for some free engineering advice from analogZONE's circuit consultant, Dennis Feucht, on how you might solve a design problem or improve circuit performance. Submissions may be edited for clarity or brevity, and submitters and their email addresses will remain anonymous (unless otherwise indicated). Please send your questions to Dennis here.

Commodity IC Data: 555

Q: I am having trouble doing detailed design of analog circuits for low-cost products using commonly-available integrated circuits. In particular, parts specifications for the 555 timer and single-supply op-amps and comparators fail to give their full functional diagrams or models of their output or input characteristics. The SG3525A PWM controller, popular for push-pull converter designs, lacks some useful design data too. Can you provide some of this information?

A: Commonly-used commodity ICs are described in the commercial literature, but these specifications sometimes do not include important design parameters. Here are some of those parameters from my investigations from using these parts in designs. In this part of a multi-part response, we look at the versatile and venerable 555 timer.

Read Dennis' entire response here (63 kb PDF file)