# Help finding type of OP Amp circuit

Discussion in 'Homework Help' started by John Di, Feb 8, 2015.

1. ### John Di Thread Starter New Member

Jan 15, 2015
3
0
Hello,
Could you help me find out what type of OP circuit this is?
I believe its an inverting circuit, but what type exactly?
Thank you very much

2. ### Jony130 AAC Fanatic!

Feb 17, 2009
4,173
1,188
Op amp in your circuit work as a voltage follower (a buffer).

3. ### MikeML AAC Fanatic!

Oct 2, 2009
5,451
1,071
It is a voltage follower with a gain of R2/(R1+R2)

4. ### Efron Active Member

Oct 10, 2010
81
15
A voltage follower" with a gain" is in this case a little bit disturbing. It is a voltage follower circuit where the output voltage of the OAMP is the same as the voltage given by the resistors divider.

5. ### Efron Active Member

Oct 10, 2010
81
15

The advantage of this circuit is that the output voltage of the OPAMP is mostly independent from the current going through the resistors. Also, the circuit on the left is not impacted by the circuit on the right due to the high impedance of the OPAMP input leads.

Note: it IS NOT an inverter. It has negative feedback so that the circuit is stable (no oscillation). This guarantees that the two inputs of the OPAMP have the same voltage value.

6. ### John Di Thread Starter New Member

Jan 15, 2015
3
0
Thanks for that, also is it a passive or active circuit, because I am having trouble distinguishing between the two. From what I read, passive circuits usually have no OP Amp but not always?

7. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,963
615
It is active. Why? Because op-amp needs external power supplies to function, these power supplies are normally not shown, but whenever you see op-amp triangle symbol, you should automatically assume that you need power supplies to power the op-amp.

Or you can approach your circuit a little differently. What you have there are actually two circuits:
1) R1 and R2 form voltage divider. This circuit is passive.
2) Op-amp is configured as buffer. X volts goes in, X volts comes out. This circuit is active because op-amp needs external power supplies.