Four quadrant voltage supply - Page 1
Forum section: electronics / projects

author: GN89
author_rank: Contributor
timestamp: August 25, 2022, 05:24:21 pm
content: For langmuir probe measurements I want to design a langmuir probe power supply for plasma density measurement. Are there any references in literature to design a four quadrant source with 300Vpp voltage swing with DC input coupling and a maximum current of 300mA source/sink. The design requirement is to use multiple lower voltage transistors in a cascade.The speed is not an issue at the moment because the plan is to sample every point and set the next voltage point. For plasma induced load regulation I think 5kHz bandwidth is more than enough for now.

author: mawyatt
author_rank: Super Contributor
timestamp: August 25, 2022, 05:42:27 pm
content: Look into a HV Op Amp like the Apex PA96. If the load can be floated then you can use a differential "H" type bridge with a lower voltage rating Op-Amp like the Apex PA107.Apex has a large selection of HV products.https://www.apexanalog.comEdit: Here's an Ap Note on using a PA441 with additional components to allow higher output currents.https://apexanalog.com/resources/articles/PSDE-Feb2014-Boost-Output-in-High-Voltage-POA-with-Current-Buffer.pdfBest

author: David Hess
author_rank: Super Contributor
timestamp: August 25, 2022, 09:55:14 pm
content: Quote from: GN89 on August 25, 2022, 05:24:21 pmThe highest power class-AB linear audio amplifiers operate in that voltage range but at much higher currents, so there is plenty of design information for that type of solution. Worst case 4-quadrant operation over the entire output voltage range is even more demanding so as you point out, a series connection of bipolar output transistors is likely required. A worst case power dissipation of 90 watts suggests that multiple parallel or series transistors should be used anyway. A power MOSFET output stage might be able to avoid a series connection.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: August 25, 2022, 11:33:16 pm
content: You might get more interesting hits if you search for SMUhttps://en.wikipedia.org/wiki/Source_measure_unit

author: Warpspeed
author_rank: Contributor
timestamp: August 26, 2022, 01:38:03 am
content: This will need more than a high voltage opamp.A hundred and fifty volts at 300mA is 45 watts dissipation.Multiple lower voltage transistors may be a solution, but beware of second breakdown issues.The safe operating area is not something to be trifled with.Its horribly stone age, but have you considered using vacuum tubes ?It should be pretty reliable and has speed potential as well.

author: mawyatt
author_rank: Super Contributor
timestamp: August 26, 2022, 02:40:41 am
content: Quote from: Warpspeed on August 26, 2022, 01:38:03 amThe mentioned Apex PA96 has a DC operating area of 70 Watts @ 300V supply, the PA93 has 125W @ 400V Supply and the PA92 80 Watts @ 400V. These are hybrid HV and HP Op-Amps specifically designed for HV HP type of uses.Check the Apex link provided above, they offer all sorts of HV, HS and HP type Op-Amps. We just evaluated the PA443 (Dual PA441), it's only 12Watts @ 350 Volts but a custom single chip MOS design, and the mentioned above App note shows how to expand the power range with a buffer. These folks are experts in this field and have been around a long time.Best,

author: GN89
author_rank: Contributor
timestamp: August 26, 2022, 11:24:43 am
content: Apex Analog was my first guess and I found the PA90 with is near the specs but the SOA tells me that it is unsafe to operate with the required operating voltage. 300mA is a very high current in langmuir probe meaurement where the wire in most cases immediately vaporizes when using standard wire strength but some corner cases require that.I'm also aware of the power dissipation that why I'm asking for literature in designing such amplifiers with multiple transistors in series. I' thinking of something like a x40 DC couples amplifier where a voltage range from an DAC is converted to -150V to +150V.

author: mawyatt
author_rank: Super Contributor
timestamp: August 26, 2022, 01:12:08 pm
content: We just completed a design beginning year that produced +-100V from a 16 bit DAC with similar precision at lower current. This was like a 128 completely independent channels (will eventually be ~1000 independent channels) AWG. Must maintain ~15 bit waveform dynamic fidelity on all channels, these are not DC but arbitrary waveforms in time and amplitude. It started out as having to produce +-150V but the requirement dropped to +-100V. This effort supported the development of a new type Phased Array Antenna based upon Liquid Crystal technology, and hopefully will evolve into a full custom chip to produce these multiple waveforms.This is why we evaluated the Apex PA441/443 and know about their HV MOS semiconductor process. If you study the App Note mentioned you'll find details on how to expand the PA441 into much higher power ranges likely compatible with your requirements if the mentioned 125W of the hybrid PA93 isn't enough.A word of caution, if you don't have experience with HV and HP devices & design, factor in various safety features such as OV and OC, as well as OT shut down. These voltage levels are lethal and at DC can sustain an arc causing fires, please be very careful!!Edit: Here's the 64 channel version, additional channels are added in 32 channel increments.Good luck and Best,

author: GN89
author_rank: Contributor
timestamp: August 26, 2022, 01:45:11 pm
content: Interesting project. Maybe the current buffer for the PA series is the reasonable way to achive the required functionality although I'm interested in how to do this without the Apex amplifiers by stacking mosfets.

author: Vovk_Z
author_rank: Super Contributor
timestamp: August 29, 2022, 12:12:03 pm
content: Quote from: GN89 on August 25, 2022, 05:24:21 pm300Vpp can be achieved without cascading.I've got several schematics which may suit TS. You just have to redesign it a bit to your actual current/voltage requirements.

author: MegaVolt
author_rank: Frequent Contributor
timestamp: August 30, 2022, 09:30:20 am
content: Quote from: Vovk_Z on August 29, 2022, 12:12:03 pmWhere did the last diagram come from? Something I don’t find it with Leonid Ivanovich

author: tszaboo
author_rank: Super Contributor
timestamp: August 30, 2022, 10:22:50 am
content: Quote from: Vovk_Z on August 29, 2022, 12:12:03 pmDid he use optocouplers to bias the FETs? That's ... That's gotta be illegal.How? But, but, but ... just how?

author: Vovk_Z
author_rank: Super Contributor
timestamp: August 30, 2022, 07:02:48 pm
content: QuoteI can't find his article at the moment. It seems to me it was somewhere in his blog (leoniv.livejournal.com. This is a russian site, and I can't go to it, many russian sites are blocked in Ukraine for spreading ru-propaganda).PS. Added later:Here I found an article from Leonid IvanovichGoogle found circuit here.

author: Vovk_Z
author_rank: Super Contributor
timestamp: August 30, 2022, 10:13:44 pm
content: Quote from: tszaboo on August 30, 2022, 10:22:50 amHere is an article with an original design.This design has the lowest frequency range among others because of optocouplers (a weak 'drivers'), but it certainly has a very big advantage of using the same type n-channel MOSFETs. It is hard or unconvenient or impossible to get complimentary high-voltage pairs sometimes. I used this circuit with +-250V and 5-15 W output and I had kind of several kiloHerts frequency range. Possibly with a very small load (milliamps) it can be faster as described in the article (20 kHz).I used both the original (staged) design and simplified by Leonid Ivanovich Ridiko (leoniv), with +-250VDC power supply. They work the same with so 'low' voltage, the latter is just simpler. Leoniv design works fine with OP37.

author: Vovk_Z
author_rank: Super Contributor
timestamp: August 30, 2022, 10:45:52 pm
content: Here in an attachments is some portion of my work with Leoniv-EDN design.Leoniv isLivhere.