Author Topic: HV Buffer Amp for AWG  (Read 2422 times)

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Offline mawyattTopic starter

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HV Buffer Amp for AWG
« on: August 09, 2021, 06:40:17 pm »
We are working on a project that requires high voltage waveforms of various types, some are custom waveforms. The available AWG we have, and the usual ones available at reasonable cost can't produce higher voltages. So we set out to develop our own, like we've done with other types of test equipment.

The package concept is based upon the low cost JunTek DPA-2698 & DPA -1698 style, these are nice low cost amps that are small, 12V powered and convenient to use. We used the readily available eBay 100m by 70mm by 35mm extruded case, end plates were replaced with custom 3D printed versions.

The electrical design uses 2 of the TI OPA462 HV Op-Amps setup for an overall gain of 10X. We also have a design based upon the APEX PA443, and another for lower voltage, higher current use based upon the LM3866, we haven't assembled these just yet tho.

12 Volt Input boost converted with a MAX1771 converter up to +-85VDC, so the output is capable of providing greater than +-80V peak signals. Low level bandwidth is >500KHz and slew rate limited to ~100KHz.

Works OK for our needs so far :-+ 

Anyway, here's what it looks like.

Best,

Curiosity killed the cat, also depleted my wallet!
~Wyatt Labs by Mike~
 
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Offline mawyattTopic starter

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Re: HV Buffer Amp for AWG
« Reply #1 on: August 09, 2021, 06:43:51 pm »
With Case. Added output spectrum at 1KHz and +34dBV (142VPP).

Best,
« Last Edit: August 09, 2021, 07:27:42 pm by mawyatt »
Curiosity killed the cat, also depleted my wallet!
~Wyatt Labs by Mike~
 

Offline joeqsmith

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Re: HV Buffer Amp for AWG
« Reply #2 on: August 09, 2021, 09:13:10 pm »
It looks so much nicer than any of my Arb interfaces.  I'm surprised that we don't see more amplifiers like this.   Maybe they are just too specialized.   I've heard of people using audio amps in some cases.   

For low frequency, high voltage, high impedance,  I've got a box with a couple of small signal transformers inside.  The outputs can run through a bridge or two sets of back to back diodes. 

I've also wanted to use my Arb and RF generators for digital work and have made various buffers using LVDS and what not.     

Many years ago I designed a small DC coupled buffer/amp using discrete transistors for low frequency use.   Picture showing a recent test with the amp on the left. 

Here it's being used to drive some speakers that were made into a poor mans vibration table.

Offline joeqsmith

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Re: HV Buffer Amp for AWG
« Reply #3 on: August 09, 2021, 11:01:07 pm »
I've shown this simple box in a few videos to demonstrate DMM's AC+DC modes.    It's nothing more than a simple line transformer and some diodes.  Back to back diodes are there to compensate for the loss in the bridge.  So it's basically full wave rectified or not rectified.   It will provide 400 VACrms with a 10Vp-p 50 ohm input. 

Offline mawyattTopic starter

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Re: HV Buffer Amp for AWG
« Reply #4 on: August 10, 2021, 12:54:51 am »
Our requirements are for DC coupling, so transformers are not an option. We also have some designs finished and the PCBs fabbed for up to  350VPP which was required initially to supply over 300VPP waveforms for our project, later we discovered we needed ~160VPP and this is why we built the OPA462 version first. The 350VPP version can also supply a 120VRMS mains waveform which may prove useful in studying the effects of 120VAC line waveforms on certain things. Here's some of these designs.

Best,
Curiosity killed the cat, also depleted my wallet!
~Wyatt Labs by Mike~
 
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Offline joeqsmith

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Re: HV Buffer Amp for AWG
« Reply #5 on: August 10, 2021, 01:08:19 am »
How much power can you get out of it at for mains work? 

Offline mawyattTopic starter

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Re: HV Buffer Amp for AWG
« Reply #6 on: August 10, 2021, 02:17:50 am »
Not that much, limited by how much current a APEX PA443 can deliver and still remain within the SOA, and within thermal limits. Our intended use does not require much current. Of course one could design a higher power/current version if the need justified, you would want a larger case & fan tho.

Best,
Curiosity killed the cat, also depleted my wallet!
~Wyatt Labs by Mike~
 

Offline joeqsmith

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Re: HV Buffer Amp for AWG
« Reply #7 on: August 10, 2021, 01:47:26 pm »
For higher power, DC coupled applications, I have used Techron.   

https://aetechron.com/index.shtml
 
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Offline mawyattTopic starter

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Re: HV Buffer Amp for AWG
« Reply #8 on: November 16, 2022, 03:04:53 pm »
Per request here's the PA443 Based HV Buffer information, note the PCB is incorrect as the PA443 A & B In/Out pinouts were hosed up. To use, carefully study the actual APEX PA443 data sheet package pinouts and the attached schematic and alter PCB layout which has the errors, please make corrections to the PCB layout before fabrication. Vaguely recall that some of the A and B amps input/outputs were swapped. Note the Gerber shown is a txt file, needs to be changed to a zip file after downloading, also the BOM is a txt file and should be changed to a CSV per EasyEDA format.

Best,
« Last Edit: November 16, 2022, 03:13:43 pm by mawyatt »
Curiosity killed the cat, also depleted my wallet!
~Wyatt Labs by Mike~
 
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Offline mawyattTopic starter

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Re: HV Buffer Amp for AWG
« Reply #9 on: July 02, 2023, 04:47:59 pm »
This is an update for another thread, but thought it better to update here. We added a surface heatsink to the PA443 package. Using the PA443 with various waveforms, note the VPP values at 270VPP.

Best,
Curiosity killed the cat, also depleted my wallet!
~Wyatt Labs by Mike~
 
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