Why would you put a 2134 in a servo application? A servo op amp should be optimized for DC operation. A 2134 is a favored amp for audio application.
Apples and oranges.
Since you replaced it, did you measure offset and drift before and after? That way you could answer your own question.
Apples and oranges.
Since you replaced it, did you measure offset and drift before and after? That way you could answer your own question.
How much offset will you allow?
According their respective data sheets:
Vio
OPA2134 +/- 2mV max
LME49720 +/- 0.7mV max
TL071 +/- 6mV max
That does not mean that they will be that much but it is what I would start looking at.
Look at the input bias current for the LME49720. I think its 10 nano amp. Sounds small until you realise it would deliver a 100mv offset with a 10meg resistor at its input. The OPA with 5pa bias current would deliver 0.05 mv under the same condition. The TL071 would be a similar ballpark figure.
However the circuit appears to use dual op-amps, so the question is very misleading.
+1
From the schematic linked, it seems like the same dual opamp is used both as output buffer and servo. So we need an opamp able to fulfill both roles.
OPA2134 seems perfectly fine here.
Look at the input bias current for the LME49720. I think its 10 nano amp. Sounds small until you realise it would deliver a 100mv offset with a 10meg resistor at its input. The OPA with 5pa bias current would deliver 0.05 mv under the same condition. The TL071 would be a similar ballpark figure.
I could not read the values in the schematic but you could use the same resistor value in each input. Old solution to old problem.
LF411 or LF412
50pA input bias current.
The lf411 isn't as good as the current opa2134 for the output buffer/filter role (higher distortion). As such, it's probably not an improvement in this particular situation.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
- Home
- Amplifiers
- Chip Amps
- Replacement for OPA2134 at DC Servo