OpAmp to provide -15V from -38V <100ma

I have two problems to solve and hopefully this can be done with a single (dual) part.

1. Supply a "clean" -15 V at about 35ma to a transimpedance amplifier from a -38V source,

2. Provide a steady-state -38V and (2) a timed sweep from 0V to around -5V.  Here, nanoamperes of current are involved.

I considered an LDO for -15, but those I can find won't take the -38V presently coming from a converter and we don't want to create another noisy switching converter!

So I'm thinking a "high output current" amplifier (dual package) powered by our available -38V (with the + rail of the amplifier to system ground) would be an option.  One of these would produce the -15V based on bias at the inverting input, and the other driving the -38V rail with a mosfet-selected triangle generator for the timed sweep.

Does Analog Devices have a suitable part for this idea.. or other ideas that will give us these voltages?

Parents
  • Harryh and Dave,

    I looked at the ADA4700-1 and considered the same concerning the current limit.  I'm powering a IVC102 transimpedance amplifier and am looking for an alternative to the +-15 v power module in our original design (12V in +-15 out with 45ma quiescent current - it's that standby current that kills us).  Although the IVC102 uses less than 35ma, some headroom would be good.  I've gone to great lengths trying to clean up both rails (LC filtering).

    So decided to stay with our module, and use the ADA4700-1 as our -38V buffer (drives a static plate, so nanoamps of current here), fed with a single -38V supply.  Rail to rail here would be 0 to -38.  Hmmm.. might I have to split the supply a bit?  I need to sweep the output from 0 (gnd ref) to -2V at a period of 60 seconds.  I suppose this can be easily done by configuring the device as an integrator.  But, from the same chip, we also need to turn on the -38V full bore.  Maybe bypass the integration cap for that move...

    Anyhow, good suggestion and one I'm planning to stick with, unless you folks have better ideas.

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  • Harryh and Dave,

    I looked at the ADA4700-1 and considered the same concerning the current limit.  I'm powering a IVC102 transimpedance amplifier and am looking for an alternative to the +-15 v power module in our original design (12V in +-15 out with 45ma quiescent current - it's that standby current that kills us).  Although the IVC102 uses less than 35ma, some headroom would be good.  I've gone to great lengths trying to clean up both rails (LC filtering).

    So decided to stay with our module, and use the ADA4700-1 as our -38V buffer (drives a static plate, so nanoamps of current here), fed with a single -38V supply.  Rail to rail here would be 0 to -38.  Hmmm.. might I have to split the supply a bit?  I need to sweep the output from 0 (gnd ref) to -2V at a period of 60 seconds.  I suppose this can be easily done by configuring the device as an integrator.  But, from the same chip, we also need to turn on the -38V full bore.  Maybe bypass the integration cap for that move...

    Anyhow, good suggestion and one I'm planning to stick with, unless you folks have better ideas.

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