Sep 14, 2012 #1 Z zhengchao201105 Member level 2 Joined Jul 11, 2012 Messages 49 Helped 2 Reputation 4 Reaction score 2 Trophy points 1,288 Activity points 1,621 I found something strange in this circuit below the sine with DC will become "pure",how does this happen? if I remove this R4,the output will "up" so what is the function of R4? Last edited: Sep 14, 2012
I found something strange in this circuit below the sine with DC will become "pure",how does this happen? if I remove this R4,the output will "up" so what is the function of R4?
Sep 14, 2012 #2 barry Advanced Member level 7 Joined Mar 31, 2005 Messages 6,343 Helped 1,194 Reputation 2,400 Reaction score 1,394 Trophy points 1,393 Location California, USA Activity points 34,548 R4 provides a DC path.The small bias current of the opamp will charge the cap otherwise.
Sep 15, 2012 #3 M maheshjalgaonkar Junior Member level 1 Joined Jan 15, 2012 Messages 15 Helped 0 Reputation 0 Reaction score 0 Trophy points 1,281 Activity points 1,371 R4 is use to discharge the capacitor forcefully so that u will get voltage starts from zero otherwise u will get voltage level to be shifted because capacitor will be charge it will not be discharge fully.
R4 is use to discharge the capacitor forcefully so that u will get voltage starts from zero otherwise u will get voltage level to be shifted because capacitor will be charge it will not be discharge fully.
Sep 15, 2012 #4 LvW Advanced Member level 6 Joined May 7, 2008 Messages 5,912 Helped 1,753 Reputation 3,512 Reaction score 1,364 Trophy points 1,393 Location Germany Activity points 40,428 For correct biasing both opamp inputs need a dc path to ground.