OPA197: Single Supply Operation

Hi Amr,

can you show a schematic?

Kai

Hi Amr,

Yes, the OPA197/OPA4197 can work with a single supply. Just need to be aware how the op amp's input common-mode voltage range (Vcm) and its output voltage (Vo) become referenced to a single supply's mid-supply point as opposed to a dual-supply ground.

There is an older Burr-Brown Applications Bulletin that should be of some help explaining how op amps can be applied using a single supply:

https://www.ti.com/lit/an/sboa059/sboa059.pdf

The OPA197/OPA4197 simulation model should function correctly. Do provide us with your simulation circuit schematic as Kai stated so that we can look for any problem it might have.

Regards, Thomas

Precision Amplifiers Applications Engineering

Hi Thomas ,

Thank you for your reply.

My input to the opamp is actually the output of AMC1200 , which is a 2V p-p signal that oscillates around 2.55V (2.55V offset)

I am using OPA197 in a fully differential amplifier configuration with 4 resistor to make the signal oscillate from 0.15 Volt to 3.15V (3 V p-p) that oscillates around 1.65V (1.65V offset) , Maybe the 150 mV is very close to the GND that's why the simulation fails ?

Do you suggest that under these conditions I could use it in dual supply configuration or is there another recommended operational amplifier similar to OPA197 that is going to work with a single supply using the same configuration and preferably P2P replacement.

Thank you very much in advance.

BR,

Amr Wael

Hi Kai ,

Here is a little bit of the schematic , I illustrated below the ranges of my signals

Hi Amr,

it can often be seen that SPice models which run properly with a bipolar supply voltage do not properly run with a single supply voltage and vice versa. And it often plays a role which simulator you use.

For me the simulation runs properly in TINA-TI:

amr_opa197.TSC

While it is true that the common mode input voltage range is not violated, your input signal runs through the critical transition region where both CMOS-FETs input pairs are on. See figure 8 and section 7.3.6 of datasheet. This can make problems in certain simulations and with certain simulators.

Another issue is the output voltage. According to the "open-loop voltage gain" specification on page 9 of datasheet, your output signal comes the supply rails so close that the output stage begins to leave the linear operating range, just as you already mentioned. This also can make issues in certain simulations and with certain simulators.

By the way, when you increase the input voltage more and more, even the above TINA-TI simulation gets convergence problems at some point and stops working properly.

There is a group of OPAmps which do not show this transition region, like the OPA325 for instance. Search for a zero-crossover device. Or stay with the input and output voltages farer away from the supply rails.

Kai

Is this issue just related to the simulator or am I going to face similar  practical problems in real-life circuits ?

Thank you very much Kai !