1/2PiRC = 0.159/RC Try it for the hipass! ----- Original Message ----- From: "Julio Jumpa" To: Sent: Monday, October 10, 2005 11:24 PM Subject: [EE] Filter question Hello, I need to build an amplifier very similar to this one i found in a book (Webster, 1995) http://img111.imagevenue.com/img.php?loc=loc256&image=c55_webster.jpg Mine needs to have a BW (-3dB) from 0.05 to 500Hz. According to this book design, the 1uF and 3,3M resistor forms a high pass filter at 0.05Hz, but 1/RC = 0.3Hz. Also, the low pass filter after that (150K and 0.01uF) is said to be at 100Hz, but 1/RC = 667Hz. Am I getting something wrong? Thanks Julio -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist