Other Parts Discussed in Thread: LMV851
in my application, I use an OPA140 configured as Voltage Follower to monitor avoltage level with a scope (HiZ input) driving a 1m-long coax cable.
The bandwidth is limited to 1MHz. Dual supply is +/- 12V.
The entire circuit is shielded in a metallic box.
Unfortunately, the (1m-long) coax cable seems injecting RF noise in the circuit, disrupting the entire circuit (a low noise voltage amplifier).
I decided to decouple the internal node from the scope by using a voltage follower. However, as matter of fact, in my case it is not enough.
The cable injects noise onto the buffer output and, somehow, it back propagates to the rest of the circuit.
I also inserted a ferrite bead at the output of the OPA, with no luck. I have seen a small improvement by inserting a 1K resistor in series
with the OPA output. I have the scope in HiZ (1M), so 1K does not change the picture.
I am wandering if the OPA140 is an 'EMI hardned' opamp or not. Devices like LMV851/861 clearly spec this feature in the datasheet. What about OPA140 ?
Should I try to redesign the PCB in order to change the OPA with the LMV ? Do you suggest other devices ?
Any advice is very welcome.