difference between the circuits

[kiranswaps]

hi friends,
can anyone please explain me the difference between the two circuits as shown in figure 1 & figure 2.

Thanks..

 

[echo47]

First one would be a non-inverting buffer, but that -15V into +V looks like big trouble.

Second one has the same suspicious power supply connection, and now you are jamming 0.5V into the op-amp's output pin. Bigger trouble.

 

[IanP]

The first picture is a voltage follower, or a non-inverting amplifier of gain=1.
Problem with the second picture is that the output is connected to input and to inverting input of the opamp. As it is, it in totally wrong configuration.
If you would like to have inverting buffer/amplifier of gain=-1 you have to place two identical resistors, first between outpit of the opamp and its inverting (-) input, second betwenn Vin and the (-) input of the opamp ..

And on top of that +V=-15V ---->big problem

 

[kiranswaps]

Thank you friends for replying.
about the reverse polarity of power supply---> actually i'm using circuitmaker to test circuits if you carefully look at the opamp the positive polarity is in downward position (acutally i rotated the opamp +mirrored).
i tried the circuit as shown in new figure. it's working fine (having a gain of 100). why are the resistors used in buffer stage. can you please explain the function of these two resistors and how are they giving a gain of -1.

lots of questions !!!!!!!! sorry, but i want to understand op-amps. i'm just a newbie.

hope you don't mind. Thanks once again.

 

[IanP]

Here you have basics on opamps:
**broken link removed**
Check pages on inverting circuit closed loop and others..
There you will find formula on the inverting opamp gain; to make it -1, Rg=Rf (see page 21)..
In your case R4=R3, so gain is (-1), then R2=100R1, so gain of the second stage is (-100).
Total= (-1)*(-100)=100

Good luck

 

[whynot910]

i think u should read some basic electronic circuits books,if u want to learn about op Amp.