Looking for advice on how to build an adjustable voltage translator. Input is standard 1V8 logic, but output HIGH is in a selectable range of +3 to -3V, while output LOW is way down in a selectable range of -15 to -21V.

Cannot find any any off-the-shelf solutions to this. Input frequency range on order of 100k square, output needs to drive upwards of 100pF. Opamps are likely to be unstable at this voltage and cap load. Ideas on types of circuits that can be used here?

enter image description here


Output side IO levels are supplies that can be set on-the-fly during operation, so the level translator needs output compliance in the shown ranges. They don't track, they are individually setable. Fast enough slew needed to reliably operate at 100k given the output swing.

  • \$\begingroup\$ The voltages on the right side, are those supply voltages? What supply voltages are available. Basically I would need to know a bit more about the circuitry connected to the right side of this level translator. The left side is clear to me. \$\endgroup\$ – Bimpelrekkie Jan 24 at 10:02
  • \$\begingroup\$ Ditto the above. You need to specify what power supplies are available. \$\endgroup\$ – Andy aka Jan 24 at 10:37
  • \$\begingroup\$ and specify min. slew rate for Ioh,Iol @ 100pF \$\endgroup\$ – Sunnyskyguy EE75 Jan 24 at 10:39
  • \$\begingroup\$ What is the compliance current requirements of the output? Basically,. I see a 6 V span for both outputs, so that suggests, if the outputs can track together, that you need an adjustable ground reference. Which can be done. But do the outputs track? Or are they independently settable? \$\endgroup\$ – jonk Jan 24 at 13:04
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    \$\begingroup\$ A comparator should work fine. \$\endgroup\$ – CL. Jan 24 at 13:31

Use an optoisolated gate driver. The isolation is kind of wasted, but much easier than cobbling together your own solution. https://www.digikey.com/products/en/isolators/isolators-gate-drivers/906

  • \$\begingroup\$ @WhatRoughBeast Is this question for me? Wrong post maybe? \$\endgroup\$ – pserra Jan 26 at 1:34
  • \$\begingroup\$ Sorry, it was intended for the OP. I've deleted. \$\endgroup\$ – WhatRoughBeast Jan 26 at 15:34

How about a video amplifier used as a comparator? I did a quick LTspice simulation with an LT1252 and it looks ok. Not what happen when it is over driven.

enter image description here

Here is the file: http://dl.free.fr/qbHDzipzS

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    \$\begingroup\$ Are you sure that V1 is supposed to be -3 volts in this configuration? \$\endgroup\$ – WhatRoughBeast Jan 26 at 15:34
  • \$\begingroup\$ @WhatRoughBeast Between -3V to +3V, based on OP's specs. -3V is the complicated case for U1 inputs range. That's why R1 to R4 are here. \$\endgroup\$ – pserra Jan 29 at 6:17
  • \$\begingroup\$ OK. But given your biasing, you don't need V4 at all. You can just ground that end and modify R1/R2 a bit. \$\endgroup\$ – WhatRoughBeast Jan 29 at 16:10
  • \$\begingroup\$ True. But in the end, Tek's solution is much better, so I'm leaving this as it is. \$\endgroup\$ – pserra Jan 30 at 2:45

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