Voltage Follower - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

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
Reply
 
Thread Tools Search this Thread
Old 30th October 2007, 03:59 AM   #1
diyAudio Member
 
Join Date: Sep 2007
Default 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.

Thanks in Advance.
Attached Images
File Type: jpg opa177.jpg (10.8 KB, 290 views)
  Reply With Quote
Old 30th October 2007, 04:08 AM   #2
diyAudio Member
 
xplod1236's Avatar
 
Join Date: Dec 2003
Location: On the couch
Send a message via AIM to xplod1236
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.
  Reply With Quote
Old 30th October 2007, 04:30 AM   #3
fdeck is offline fdeck  United States
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.
  Reply With Quote
Old 30th October 2007, 03:26 PM   #4
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
File Type: jpg opa1771.jpg (9.0 KB, 194 views)
  Reply With Quote
Old 31st October 2007, 04:37 PM   #5
AndrewT is online now AndrewT  Scotland
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.
  Reply With Quote
Old 1st November 2007, 08:08 AM   #6
diyAudio Member
 
Join Date: Sep 2007
I see. Thanks for you help.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

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 Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
best voltage follower, discrete opamp and whatnot gearheadgene Solid State 79 5th July 2008 12:28 PM
Resistive ps voltage follower av-trouvaille Tubes / Valves 22 6th April 2008 08:28 PM
Sziklai emitter follower as voltage stabilizer hjelm Solid State 23 25th May 2004 04:09 PM


New To Site? Need Help?

All times are GMT. The time now is 05:16 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2