TLE2061: Alternate

Hi Shihab,

hmm, the TLE2061AM has a moderate open loop output impedance. 280R isn't much. How does it affect your application?

Kai

Hi Shihab,

The OPA172 or TLV172 is where I would start, but it has higher Iq than the TLE2061AM. Can you provide a little more information on your application? What type of circuit is this? We might have offerings in both our Precision Amps and Audio Amps portfolio that will better meet your needs.

Best,
Paul

Hi Kai, Paul,

This is an op-amp buffer circuit to drive a capacitive load.
I have used a multi feedback circuit to make the circuit stable (phase margin >45deg) for a particular cable length.
But recently I had to reduce the cable length and found that the phase margin went below 45deg because of the reduction in cable capacitance.
Increasing the isolation resistor in the multi feedabck compensator will help to increase the phase margin >45 but I cannot do it as I will not get enough voltage across the sensor (Under worst case condition) as the opamp may go to output saturation. The next possible solution is to add additional capacitor at the output to match the earlier cable capacitance value. Another possible option is to replace the op-amp with another having lower open loop output impedance . I already have the PCB built so i cannot add anymore additional components for compensation.

Thanks,
Shihab.

Shihab,

Could you attach an image of the relevant portion of the schematic? My thought is that you could try to use something like Riso with dual feedback as demonstrated in this video: training.ti.com/ti-precision-labs-op-amps-stability-6 and adjust the components to get more phase margin. I know you said that your board is built, but you may be able to make this work with the component spaces you have.

Even with your topology, don't you have other points of adjustment than just the isolation resistor? Usually the multiple feedback topologies rely on poles/zeros set by resistor/cap pairs that could be adjusted for greater phase margin.

"Increasing the isolation resistor in the multi feedback compensator will help to increase the phase margin >45 but I cannot do it as I will not get enough voltage across the sensor (Under worst case condition) as the opamp may go to output saturation. "
--> Can you detail this worst case condition?

You could give up a little on supply current which really does open your options to other devices like the OPA145, OPA180, OPA171, and OPA172.

-Paul

Hi Shihab,

yes, show us a schematic.

Kai

Hi Kai, Paul,

Following is the example simulation screen shot. Here with C3=10nF, the circuit is stable having >45degree Phase margin.

But when C3 is reduced to 1nF, due to cable length reduction, then the Phase margin drops below 45degC.

Please note that I cannot increase R3 further. The maximum frequency of the output signal will be 4.5KHz.

I see that, one of the option to regain phase margin is to put additional capacitance of 9nF across C3.

Is there any other way you see without adding additional components?

Hi Shihab,

I would add a snubber:

shihab1.TSC

Kai

And take care, the TLE2061 has an open loop output impedance of 280R. But the TLE2062 has an open loop output impedance of 560R!

Kai

Hi Kai,

Earlier I had posted a question about the open loop output impedance of TLE2061 and TLE2062.

The response that I got was, TLE2061 and TLE2062 uses the same output stage so the Zo should be the same.

Thanks,

Hi Kai,

Do you see any issue if I add only output capacitor (instead of RC snubber)? It will result in reduced bandwith of circuit. But as the max frequency of output is <5KHz, I don't see any issue in using only 10nF capacitor and not 47ohm resistor in the snubber.

Thanks,
Shihab,