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I am trying to terminate the unused unity-gain unstable op-amp. I have tried to terminate it with the typical unity-gain stable configuration (http://www.maximintegrated.com/en/app-notes/index.mvp/id/1957) and so far in the lab, it seemed to work and gave stable output. However, I am still concerned about it as it is unstable at unity-gain region mentioned in datasheet. I want to learn if there is anything more robust than using unity-gain termination configuration. The amplifier I am using is OPA2614 from TI. So far I have tried this to stabilize the output at 12V but don't know if this is the best way.: enter image description here

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  • \$\begingroup\$ @SpehroPefhany yes, I did accept the answer to the related question before but then I still got a bit confused to understand why bias inputs to 100mV<V<300mV rather than GND for -V and 6V for +V? Moreover, I wanted to understand how bad is it to use unity-gain termination with DC input on unity-gain unstable amplifier. I want to know more reasoning behind this specific question. \$\endgroup\$ – dr3patel Jul 6 '15 at 2:19
  • \$\begingroup\$ Okay, you should have at least one (preferably both) inputs within the common mode range of the amplifier if you want to use this method. That means more than +1.6V with this particular part. See the datasheet. \$\endgroup\$ – Spehro Pefhany Jul 6 '15 at 2:34
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    \$\begingroup\$ The link you provided recommends against keeping the output unconnected. Have you considered using the first circuit in the link? That op amps is connected in feedback configuration, which yours seems not to be. \$\endgroup\$ – avl_sweden Jul 6 '15 at 13:16
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This would be better (output left open):

schematic

simulate this circuit – Schematic created using CircuitLab

Both inputs are within the common-mode range of the amplifer- see the datasheet which gives the values with a +/-6V supply and translate by adding 6V to the numbers.

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