OPA564: Check the Load Capacitance

Louis Han15

Genius 4680 points

Part Number: OPA564

Hello

Oscillation is occurring due to the load capacitor of the OPA546 output stage.

I attached the Simulation file.

1. Do you any recommended load capacitor capacity for remove the oscillation?

2. Do you oscillation data provided according to the load capacitor?

OPA564_200822.TSC

Best regards

over 5 years ago

0 Raymond Zhang1 over 5 years ago

TI__Guru* 77521 points

Hi Louis,

Op Amp does not like to drive larger capacitive load. With 300nf capacitive load, the feedback loop has to be compensated. Enclosed is the compensated loop that should be stable with 300nF capacitive load.

The following circuit will have unity gain BW at approx. 679kHz with phase margin of 72 degree.

/cfs-file/__key/communityserver-discussions-components-files/14/OPA564_5F00_200822-modified.TSC

If you have any other questions, please let us know.

Best,

Raymond

0 Thomas Kuehl over 5 years ago

TI__Guru* 93105 points

Hello Louis,

The OPA564 is likely to oscillate with the three, 100 nF capacitors connected from the output to ground due to phase margin degradation. That is a common behavior for most op amps when they are pressed to drive a high capacitance load. Added the appropriate compensation should eliminate the oscillation.

What kind of load must the OPA564 drive besides the three, 100 nF capacitors? Can the output signal path tolerate a couple of Ohms of series resistance, or would the voltage drop be an issue? There are several different compensation methods that we can consider if a simple, series output resistance isn't doable.

Regards, Thomas

Precision Amplifiers Applications Engineering

Amplifiers

Amplifiers forum

OPA564: Check the Load Capacitance