Question: I need to terminate an unused op amp and plan to use the [recommended circuit](https://youtu.be/gwQiFuckMz0?t=727) below with +3.3V. How do I choose the resistor values? The op amp I'm using is the [MCP6002](https://www.microchip.com/en-us/product/MCP6002) ([datasheet](http://ww1.microchip.com/downloads/en/DeviceDoc/MCP6001-1R-1U-2-4-1-MHz-Low-Power-Op-Amp-DS20001733L.pdf)).

[![](https://i.stack.imgur.com/gY6Ji.png)](https://i.stack.imgur.com/gY6Ji.png)

I understand too low allows a lot of current, wasting power. Too high and it's not enough current to drive the load. In this case the load is just the op amp. Here is where I get lost. What determines a reasonable but low amount of current to put through the op amp?

`Output Short-Circuit Current` is +/-6mA @ 1.8V, so something like < 3mA @ 3.3V would be very safe for the high end, but I want the low end.

10K ohms for both resistors would be 0.33mA. I guess that would be fine, but can I go lower?

Answer: 
The op-amp has rail-to-rail input capabilities hence, you can tie the unused input to either: -

* 3V3 or
* 0 volts

Noting this from the DS: -

[![enter image description here](https://i.stack.imgur.com/T7p9M.png)](https://i.stack.imgur.com/T7p9M.png)

I'd probably tie IN+ to 0 volts.

> 
> *What determines a reasonable but low amount of current to put through
> the op amp?*
> 
> 
> 

Well, the graph above gives some indication but, unfortunately, the DS doesn't give an equivalent graph when the input is close to the positive rail.

If you insist on using a potential divider, take note that the input bias current is about 1 nA over temperature and, if your resistors were 1 MΩ roughly, that would mean a 1 mV drop across them so, I'd go as high as possible because it won't really matter that much.
The voltage divider has the purpose of guaranteeing a voltage on the IN+ that is within both the input common-mode voltage range and the output voltage range. Mid-supply is a safe bet but not a must.

If you use resistors, use the largest resistor present in your BOM. That way, the least amount of current from the supply rail will be wasted. The "op amp load" has nothing to do with these resistors, it has no load being connected only to one MOSFET gate.

The datasheet section 4.5. recommends an alternative solution with no additional components but this one is not recommended as it can cause increasing supply current (out-of-spec even), (more discussion [here](https://electronics.stackexchange.com/questions/576556/unused-opamp-termination-how-does-it-cause-increased-current-consumption?noredirect=1&lq=1)).

[![enter image description here](https://i.stack.imgur.com/YWCA1.png)](https://i.stack.imgur.com/YWCA1.png)

Instead, another solution that is safer and also requires no components, is to connect the output of the used amp in the package to the IN+ of the unused one. This assures that the unused one is always kept at a safe voltage, assuming the used amp's circuit is proper.

![schematic](https://i.stack.imgur.com/274Ck.png)

[simulate this circuit](/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2f274Ck.png) – Schematic created using [CircuitLab](https://www.circuitlab.com/)