BUF634A: Paralleling devices

you would be better to use the OPA2677 dual CFA line driver in a unity gain configuration, it can actually put out over 1A in each of the two devices of this dual. This is an early DSL line driver where it was not completely clear how much current we needed. So, the K.20 testing needed to absorb over 1.5A and this part did very well as it could do that (kind of by accident)

Of course, the 12V OPA2677 can't do as much voltage swing as the BUF634A,There are 30V DSL line drivers also that put out quite a lot of current as well, but no where near the OPA2677

We have already considered OPA2670 which is similar to OPA2677 but we rejected it due to its capacitive load restrictions. The capacitive load can vary widely in our application and the series resistor value suggested in the datasheet is too big for the output current which we need. 

Is the suggested series resistor value required for general amplifier stability? If the series resistance would be smaller, do we risk instability, or just some gain peaking?

Well Michal, can't go much further without the cap load range, desired speed and signal swing

We need cap load range is from 100 pF to a 10 uF, frequencies up to 50 kHz for low capacitances and 10 kHz for high capacitances, amplitude +-3 V. Our simulated circuit with four BUF634As in parallel seems to meet such criteria, but we need to know if it safe to use it in this way.

Hi Michal,

Using a buffer in a parallel configuration can be implemented. One concern from the values you presented is the current required specifically in the 10uF condition. I will attach an article that highlights the use of parallel BUF634 devices and performance considerations that can be applicable to your application. 

Combining_an_Amplifier_with_the_BUF634 (ti.com)

Best Regards,

Ignacio