This thread has been locked.
If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.
Part Number: INA111
Hi,We are considering using this device.While checking the graph information, I found a peculiar characteristic.Could you tell me about Gain vs Frequency graph?1.The amplification factor increases in the range of 1MHz to 2MHz under the condition of "Gain = 1".Is this phenomenon unique to INA111?Could you tell me the reason why the amplification factor increases at the point of "⓵"?And Does this increase phenomenon depend on individual differences and temperature?2.Under the condition of "Gain ≥ 10", the amplification factor increase phenomenon does not occur.Is there any reason why the increase phenomenon does not occur at the "②" point?Is it possible that it will occur due to temperature or individual differences?Best regards,Yusuke
Q: Is this phenomenon unique to INA111?
Could you tell me the reason why the amplification factor increases at the point of "⓵"?And Does this increase phenomenon depend on individual differences and temperature?
All instrumentation amplifiers have this phenomenon at lower Gain (Gain=1). The point of interested in Q or gain peaking is resulted from feedback resistor (25kOhm) interacting with the input and output capacitance, typically in an order of 1-2pf, which it introduces a second pole near the corner frequency. I do not have data to present the temperature effects on the Q, but it is believed that the effect is minimum. I do not have the information of op amps used in INA111 part.
I am demonstrating the phenomenon with a known OPA192 op amps, you can see the effect via simulation. In addition, the bode plot in the last stage differential op amp is products of the analog front end in 3-op amp Instr. configuration. Typically, the front end op amps use high BW types because of high gain requirements in instr. amplifier.
Q: Under the condition of "Gain ≥ 10", the amplification factor increase phenomenon does not occur.Is there any reason why the increase phenomenon does not occur at the "②" point?Is it possible that it will occur due to temperature or individual differences?
When instr. gain increases, two things are happening. The cutoff frequency is lowered due to GBP, and the two poles starts to separate due to lower Rg value. So the Q effect starts to minimized in higher gains (Q<1).
I am enclosing the Tina simulation and you may be able to understand the interaction better, if you perform the simulation.
If you have additional questions, please let us know.
We are glad that we were able to resolve this issue, and will now proceed to close this thread.
If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.