I need to amplify a weak signal(few nanovlts) from solenoid to few hundred millivolts. I am working on an energy harvesting device but I am unsure of the output since the DAQ(HP 34970 A) works in range of millivolts. So is there any amplifier which I can use for this purpose? I had read a few suggestions about using op amp 741 and op amp LT1028.


closed as unclear what you're asking by Marcus Müller, Olin Lathrop, Transistor, Voltage Spike, uint128_t Apr 5 '18 at 23:35

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ No, you don't, or not unless much ado: this is extremely hard, and usually only possible when you know a lot about the signal you want to amplify, because noise voltages will probably be significantly higher than nV. So, describe your overall problem instead of what you think solves it. Designing a low noise, high gain amplifier is way harder than you might think, and you'll have to restrict what you're amplifying to even make it theoretically possible! \$\endgroup\$ – Marcus Müller Apr 5 '18 at 18:28
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    \$\begingroup\$ Also, at nV, we're getting dangerously close to regions where physics starts to get strange, so I'm almost certain that either you're an experimental physicist with an expensive problem, or chasing ghosts. Either way, I'll have to vote to close this question unless you clarify the overall purpose, and what your solenoid is picking up. \$\endgroup\$ – Marcus Müller Apr 5 '18 at 18:33
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    \$\begingroup\$ Do you want to amplify a signal, or are you harvesting nV but need mV for your IC? \$\endgroup\$ – PlasmaHH Apr 5 '18 at 18:41
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    \$\begingroup\$ The LT1028 is profoundly better than the ancient 741 op-amp. You may need two stages to amplify 1,000 times. Without details any more would be just guessing. \$\endgroup\$ – Sparky256 Apr 5 '18 at 18:53
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    \$\begingroup\$ If you are harvesting energy, then an amplifier won't help. An amplifier has to draw power from somewhere else. If you could use an amplifier to get more power without having to provide power the amplifier then you would have a perpetual motion machine. And hobbyists and engineers would have been building them since forever. \$\endgroup\$ – JRE Apr 5 '18 at 19:33

I need to amplify a weak signal(few nanovlts) from solenoid to few hundred millivolts.

You are chasing at shadows. There is probably no signal there at all.

Nanovolts (10-9 V) are ridiculously small units. There are numerous sources of experimental error which can produce voltages in even the µV range, including:

  • Thermal noise.
  • Current induced in your test leads by nearby devices (e.g, a cell phone, a computer, fluorescent lighting, or the measuring instrument itself).
  • Electrochemical potentials created by differences in metal composition between your test leads and probes, the jacks in the measuring instrument, and/or the devices they are probing.

No amount of energy harvesting can turn a nanovolt potential into useful energy. An amplifier is certainly not helpful, as it requires an electrical input to perform amplification.


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