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I am working on a project in which a very high negative voltage is required. I have the following equipment

  • DC power supply with max output voltage of 300V

  • Function generator with a maximum peak-to-peak voltage output of 20 Vp-p

  • An electric probe, which is essentially a wire

I would need to control the electric potential of the probe using a sinusoidal waveform. For example, the waveform may have a frequency in the range of 30-50 Hz, a peak-to-peak voltage of about 150 Vp-p, and reach a DC offset of -300 V. It is important to reach voltages of about -350 V.

I was wondering if using a linear operational amplifier (op-amp) would be a doable way to create a waveform similar to the one described above.

Essentially, to use a function generator to create a signal (e.g., a sine wave of 30-50 Hz, DC offset of -20 V, peak-to-peak voltage of 20 Vp-p) and amplify the signal with an op-amp having a gain of 10. The output signal would have a same frequency, DC offset of -200 V, and peak-to-peak voltage of 200 Vp-p.

Is it possible to achieve those negative voltages with an op-amp? If yes, are there off-the-shelf op-amp able to do so?

EDIT The output current is 50 mA, at most.

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  • \$\begingroup\$ I doubt you will find off the shelf opamps for this. I'd use a discrete amp. How much output current do you need? \$\endgroup\$ – peufeu Apr 17 '17 at 22:48
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    \$\begingroup\$ Apex Microtechnology makes high voltage and high power op-amps \$\endgroup\$ – Peter Bennett Apr 17 '17 at 22:49
  • \$\begingroup\$ If I understand you correctly, an op-amp will not do the job. An op-amp can only output as high or low as you have supply voltages; to get an output that hits -350V you need to supply -350V (or more (as in less, say -360V) ) \$\endgroup\$ – Orotavia Apr 18 '17 at 3:21
  • \$\begingroup\$ @peufeu The output current is 50 mA, at most. \$\endgroup\$ – Zeta Apr 18 '17 at 12:44
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Why not use a transformer?

Put your signal into the primary. Put your DC to one side of the secondary and "Ground". Measure your resulting signal with offset on the other side of secondary and ground.

If there is no DC Current then the transformer wont get all unhappy and saturated with consequent wave distortion.

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