Voltage Follower - diyAudio
 Voltage Follower
 User Name Stay logged in? Password
 Home Forums Rules Articles The diyAudio Store Gallery Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Chip Amps Amplifiers based on integrated circuits

 Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
diyAudio Member

Join Date: Sep 2007
Voltage Follower

Hi i am quite new in here. Nice meeting you all.

There is something i would like to ask you all. I am quite confuse with this Op-Amp.
From the pic 1, i understand that its a voltage follower itself since i check from the web. But i don't understand from pic 2 when you add 2 10k ohm resistors its still a voltage follower. Then whats the use of the 10k ohm resistor if its already a voltage follower.

Attached Images
 opa177.jpg (10.8 KB, 294 views)

 30th October 2007, 04:08 AM #2 diyAudio Member     Join Date: Dec 2003 Location: On the couch The first one is a 1:1 voltage follower; you feed it 1v, it puts out 1v. The second is a 1:-1 follower; you feed it 1v, and it puts out -1v.
 30th October 2007, 04:30 AM #3 diyAudio Member   Join Date: Feb 2006 Location: Wisconsin In the second case, the + input of the op amp should be grounded. There is a useful rule of thumb: "The op amp does whatever it can to make its inputs equal." In the first circuit, it is a follower because the inputs are equal if the output equals the + input. In the second circuit, the + input is grounded, so the op amp has to hold the - input at ground potential. It does this if the voltages at the ends of the two resistors are equal but of opposite polarity. That's how the second circuit achieves an output equal to the negative of the input.
diyAudio Member

Join Date: Sep 2007
From what you say about second test is becuase i put the input in the negative side that why the output provides a negative right. Then what do the resistors are for?

The circuit should look like this.
Attached Images
 opa1771.jpg (9.0 KB, 198 views)

 31st October 2007, 04:37 PM #5 diyAudio Member   Join Date: Jul 2004 Location: Scottish Borders no, remove the 10k pot, just connect the non-inverting input to signal ground. However, the unmatched resistances seen by the two opamp inputs will generate an output offset. To minimise the output offset, the resistor between non-inverting input and signal ground should be 10k//10k =5k0. The two 10k resistors set the gain of the inverting stage. gain=-Rfb/Rin=-10k/10k=-1. Zin =10k, Zout is very low. This inverting circuit can have a gain greater than -1, or by changing the resistors, a gain of less than -1. The non-inverting opamp can only have a gain of greater than 1. __________________ regards Andrew T.
 1st November 2007, 08:08 AM #6 diyAudio Member   Join Date: Sep 2007 I see. Thanks for you help.

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are Off Refbacks are Off Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post gearheadgene Solid State 79 5th July 2008 12:28 PM av-trouvaille Tubes / Valves 22 6th April 2008 08:28 PM hjelm Solid State 23 25th May 2004 04:09 PM

 New To Site? Need Help?

All times are GMT. The time now is 07:53 AM.

 Home - Contact Us - Advertise - Rules - Store - Sponsors - Archive - Privacy Statement - Terms of Service - Top - Opt-out policy

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.