> have anybody heard anything about amplifier circuit using hex > inverter chip and other discrete ? where can i find more info ? > thanks in advance You need to use a feedback resistor (from output to input) of a meg or two, to get the inverter into its linear region. They can be quite sensitive and a bit "twitchy" -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body