Function Generator Amplifer // extending the output voltage range - Page 1
Forum section: electronics / beginners

author: danielbriggs
author_rank: Regular Contributor
timestamp: June 06, 2021, 03:17:11 pm
content: Hi there,Perhaps a basic question, but can anyone advise me of how best to "extend" / amplify the output range of my Siglent SDG2122X?That is 0-20V pk-pk with a ±10V DC offset and is great for 99% of things I've used it for. However I'm looking at doing some projects that require a voltage range outside of this. (The liquid crystal shutters need ~30-35V pk @ 2khz)It would be super useful in the early stages of learning+playing around to use my function gen, but over a broader voltage range.Are the any reccomended amplifers that aren't bank-breaking I could use on the output of my Siglent to stretch the range to 0-50V?There are also some projects I'm potentially planning involving piezos I might need 0-75V and 0-150V function gen if the same equipment or a variant can be used over this greater range too that'd be great!The current consumption at this higher level is fairly low <20mA.I'd only need for the LCD experiments, ~2-10kHz of bandwidth, but would be interested in getting a solution with signficantly higher bandwidth should I need it in the future. Ideally something matching the 120MHz of the function gen would be ideal, if a little overkill.Needed as a min 1 channel, but 2-channel amps might be worth looking at for future use if they're common?I did find the Keysight 33502A, but this is way out of budget!https://www.keysight.com/gb/en/assets/7018-02344/data-sheets/5990-4826.pdfI don't particularly fancy rolling my own op-amp solution, and would rather for speed buy a piece of test gear, new or used that's fairly decent if anyone can reccomend any such kit to go eBay hunting for?Thanks in advance.Dan

author: bdunham7
author_rank: Super Contributor
timestamp: June 06, 2021, 04:06:34 pm
content: Feeltech, Juntek and others have these linear amplifiers on eBay, AliExpress, etc with various specifications. Here's one that would work with your current project, with up to 140Vp-pin single channel dual-differential mode (essentially bridged) up to 100kHz. It puts out decent current as well.https://www.ebay.com/itm/353344861197?hash=item5244feb40d:g:gREAAOSwpLJf9rOfGreater bandwidth generally would mean less power. 150Vpk@ 120MHz would be quite extraordinary, expensive and probably dangerous. That's solidly in RF power amp territory.

author: tautech
author_rank: Super Contributor
timestamp: June 06, 2021, 11:48:44 pm
content: There is a Siglent accessory for this: SPA1010Some info here:https://int.siglent.com/products-ware/sdg2000x/#navsMore:https://siglentna.com/product/spa1010-10-watt-amplifier/

author: ledtester
author_rank: Super Contributor
timestamp: June 07, 2021, 12:14:00 am
content: For audio frequencies, what about just using a stereo amplifier?

author: BeBuLamar
author_rank: Super Contributor
timestamp: June 07, 2021, 12:22:07 pm
content: Quote from: tautech on June 06, 2021, 11:48:44 pmThe OP wants DC offset capability and I doubt that an audio amplifier would like that.

author: danielbriggs
author_rank: Regular Contributor
timestamp: June 07, 2021, 12:28:06 pm
content: Quote from: bdunham7 on June 06, 2021, 04:06:34 pmThanks all,Those units look like they might do the job nicely!Much appreciated.All the best,Dan

author: mawyatt
author_rank: Super Contributor
timestamp: June 07, 2021, 06:39:36 pm
content: Check out JunTek DPA -1698 and DPA 26-98, or DIY if you need very high voltage like up to +-175V.Best,

author: mawyatt
author_rank: Super Contributor
timestamp: June 07, 2021, 06:46:23 pm
content: Hear's another HV amp based upon the OPA454, or OPA462 for +- 90V.Best,

author: mawyatt
author_rank: Super Contributor
timestamp: June 07, 2021, 06:53:23 pm
content: Or higher power, lower distortion version based upon LM3886.Best,

author: danielbriggs
author_rank: Regular Contributor
timestamp: June 07, 2021, 07:01:22 pm
content: Thanks Matt!Some incredible DIY options there I might explore! Thanks so much for sharing.Do you happen to have any of those gerbers on a github account or similar?All the best,Dan

author: mawyatt
author_rank: Super Contributor
timestamp: June 07, 2021, 07:21:02 pm
content: Sorry no GitHub account.Haven't had time to order the PCBs yet, but did get most of the parts in. These are all designed to fit in the popular 100-75-35mm aluminum extruded cases available on eBay, they also support a 30mm square fan that fits vertically in the PCB slot. This was copied from the way the JunTek amps are supplied, we have both and they are pretty good but have limited voltage, and why we developed these alternatives.Here's images of the JunTek and case mentioned. BTW these were specifically designed to work with the Siglent AWG (SDG2042X) since we required higher voltage and currents for some of the research work (piezo electric & voice coil stages for example) we were involved with.Best,Mike

author: MathWizard
author_rank: Super Contributor
timestamp: June 09, 2021, 03:45:10 pm
content: So could you just take a push-pull amplifier designed for the appropriate frequency, and then just drive it w/ the Siglent ?I should try making such a thing, at least up to audio frequencies shouldn't be so hard with cheap parts I have on hand.

author: mawyatt
author_rank: Super Contributor
timestamp: June 10, 2021, 12:36:08 pm
content: The fundamental problem with push pull or H bridge amps is they can't drive a single ended load, and outside of audio speakers and motors most devices are single ended. They also have higher distortion, can be unstable and don't work well at higher frequencies. They are nice for certain type loads as mentioned, but not a good general purpose solution.The load we are working with now requires a high voltage bipolar signal but is single ended, and why the HV AWG amps mentioned above are going to be assembled. The previous piezo electric stages were floating. We developed a full custom (mostly discrete) designed amp, and could not use the HV IC versions shown because of load (many uF capacitance), and the precision. This full custom design involved a closed loop system (flexure bearings) with the dual bridge type position sensors in the feedback loop, a current mode output for stability, and achieved measured nanometer resolution.BTW you could use the dual outputs of the AWG Amp as a bridge amp. Set the AWG channels up as + and - waveform and connect floating load between dual outputs from the AWG or Dual Amp, should work, although we haven't tried.Best