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current buffer with buf634 unity gain

shimon akrish
Prodigy 110 points

Other Parts Discussed in Thread: BUF634

Hello,

I'm planning on using the buf634 as current buffer inside an opamp loop as described in the datasheet in figure 24.

In my application the buffer will be connected to +/-15v supply with +/-11.8v 400hz input

The output current can reach 220mA

According to the datasheet the output voltage swing decreases with temperature and output current so I thought on paralleling two buffers.

I know there is issues with connecting opapms in parallel as described in:

e2e.ti.com/.../paralleling-op-amps-is-it-possible

But is there problem with paralleling buffers inside unity gain opamp loop?

I have attached my pspice circuit which worked fine in the simulation.

  • 0
    TI__Guru* 93105 points

    Hello Shimon,

    Like power op amps, paralleling BUF634 buffers should be doable. The main concern when doing so is that the op amps/ buffers may have different voltage offsets and their output voltages will be different from each other resulting in unnecessary current exchange between outputs and increased power dissipation. Bruce Trump explains this behavior in the E2E blog you have cited. Therefore, use the master/slave configuration with the series output resistors shown in the blog. 

    I did find a couple of applications on line that show two, or more, BUF634 buffers using this kind of configuration. The first is a TI E2E discussion:

    And this is an application from Japan:

    The Spice simulation would work perfectly because the two BUF634 simulation models would have exactly the same voltage offset and are identical for every other electrical parameter. That is unlikely to be the case for real BUF634 devices.

    Regards, Thomas

    PA - Linear Applications Engineering