hi every body! i've made an ultra sonic transmitter. the signal is made by LM55 an for amplifying the current i've used a 7400 gate nand. at the end the output of 7400 is send to the sonar. it worked properly and i got the signal with my receiver. but now after one day, my signal has a lot of noise. when i unplug the NAND the noise is no more there!!! why??? [Non-text portions of this message have been removed]
Message
a problem with 7400 NAND
2011-08-14 by Sh R