Author Topic: Amplifier for Function Generator needed (500 mA)  (Read 9783 times)

0 Members and 1 Guest are viewing this topic.

Offline HighVoltageTopic starter

  • Super Contributor
  • ***
  • Posts: 5453
  • Country: de
Amplifier for Function Generator needed (500 mA)
« on: September 22, 2018, 01:02:24 pm »
I am looking for a simple amplifier to gain the current output of a Keysight function generator.

- Voltage output: 10V PkPk
- Current output: 500 mA
- Max Frequency: 100 kHz

What do any of you use?
What is of the shelf available?
Any recommendations?

I found the LPA01 from Newtons4th but what else is available that will not break the bank?

There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline T3sl4co1l

  • Super Contributor
  • ***
  • Posts: 21606
  • Country: us
  • Expert, Analog Electronics, PCB Layout, EMC
    • Seven Transistor Labs
Re: Amplifier for Function Generator needed (500 mA)
« Reply #1 on: September 22, 2018, 01:38:26 pm »
Almost any audio amp circuit or buffer IC will do.

Building, or off-the-shelf, plug and go?

Tim
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 

Offline HighVoltageTopic starter

  • Super Contributor
  • ***
  • Posts: 5453
  • Country: de
Re: Amplifier for Function Generator needed (500 mA)
« Reply #2 on: September 22, 2018, 01:56:45 pm »
Thanks, This is for official use and I need an amplifier with datasheet that can be calibrated.
So, DIY is not applicable for this project.

I just came across the RIGOL PA1011, a 10W Power Amplifier for around $ 400
May be this can work.

There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline maukka

  • Supporter
  • ****
  • Posts: 107
  • Country: fi
 

Offline JohnPi

  • Regular Contributor
  • *
  • Posts: 158
  • Country: us
Re: Amplifier for Function Generator needed (500 mA)
« Reply #4 on: September 22, 2018, 02:15:50 pm »
Does anyone have any experience with that one ? Is it current limited ? Is there just a stereo amplifier inside the box ?
 

Online Kleinstein

  • Super Contributor
  • ***
  • Posts: 14073
  • Country: de
Re: Amplifier for Function Generator needed (500 mA)
« Reply #5 on: September 22, 2018, 03:50:03 pm »
Does anyone have any experience with that one ? Is it current limited ? Is there just a stereo amplifier inside the box ?

I don't think they would use a stereo amplifier - more like a mono audio amplifier chip. It may be a more modern one to get at least a reasonable speed and have some protection. For just 50 kHz there is no need to do it different.
 

Offline TurboTom

  • Super Contributor
  • ***
  • Posts: 1388
  • Country: de
Re: Amplifier for Function Generator needed (500 mA)
« Reply #6 on: September 22, 2018, 09:19:24 pm »
What about the EvilAmp?  >:D
30Vpp and 10A up to 10MHz (probably got to use a PL239 as the output connector...)

Just kidding, this would be way beyond your requirements and it's not available as a finished unit. But it may be interesting for some anyway. It's based on ten cascaded LT1210 wideband power opamps that have been matched for offset voltage. The PCB is single sided aluminium substrate. To be able to design the whole unit on a single-sided board, I had to use the substrate (and the underlying heat sink) as the ground plane. That's why there are so many M2 screws holding the assembly down. Each of these screws provides a ground connection. Proper heat sinks are underway and the power supply still needs to be designed. Currently I'm running it off a Lab supply but that's marginal for the substantial power demand of this amp. So far, everything's really looking good and the unit performs as designed. I've got to complete the new PSU soon to be able to test it at full grunt... Once finished, I may publish some more detailed design information in case someone wants to duplicate it  ;)

Cheers,
Thomas
« Last Edit: July 26, 2019, 08:15:34 pm by TurboTom »
 
The following users thanked this post: nctnico, TiN, thm_w

Offline JohnPi

  • Regular Contributor
  • *
  • Posts: 158
  • Country: us
Re: Amplifier for Function Generator needed (500 mA)
« Reply #7 on: September 22, 2018, 09:52:34 pm »
Does anyone have any experience with that one ? Is it current limited ? Is there just a stereo amplifier inside the box ?

I don't think they would use a stereo amplifier - more like a mono audio amplifier chip. It may be a more modern one to get at least a reasonable speed and have some protection. For just 50 kHz there is no need to do it different.

The pictures show OUT+ and OUT-. My guess is that it uses a stereo audio amplifier in a bridge configuration; but I'd like to know how this is configured, and if it works well (ringing, slew-limiting) and if there is short circuit protection.
 

Online Wolfgang

  • Super Contributor
  • ***
  • Posts: 1773
  • Country: de
  • Its great if it finally works !
    • Electronic Projects for Fun
Re: Amplifier for Function Generator needed (500 mA)
« Reply #8 on: September 22, 2018, 11:33:21 pm »
Hi,

have a look at the Jim Williams Appnote "High Speed Amplifier Techniques".
He describes some amps with +/-10V output, frequency from DC to a few MHz and 1A output.
Another interesting note is "Gain Stages for Monolithic Amplifiers" by the same author.
I built some of those and they are stable and fast.
 

Offline maxwell3e10

  • Frequent Contributor
  • **
  • Posts: 869
  • Country: us
Re: Amplifier for Function Generator needed (500 mA)
« Reply #9 on: September 24, 2018, 04:25:17 am »
What about the EvilAmp?  >:D
30Vpp and 10A up to 10MHz (probably got to use a PL239 as the output connector...)
Cool! I could use something like this
 

Offline DaJMasta

  • Super Contributor
  • ***
  • Posts: 2289
  • Country: us
    • medpants.com
Re: Amplifier for Function Generator needed (500 mA)
« Reply #10 on: September 24, 2018, 04:41:18 am »
Maybe you could find a low frequency, high power RF amp rated for +33dBm output power instead?  I don't know of a lot of premade options for this kind of amp, but perhaps one of these inline RF amp modules would qualify for being characterized and otherwise official.
 

Offline TurboTom

  • Super Contributor
  • ***
  • Posts: 1388
  • Country: de
Re: Amplifier for Function Generator needed (500 mA)
« Reply #11 on: September 24, 2018, 05:53:47 am »
Maybe you could find a low frequency, high power RF amp rated for +33dBm output power instead?  I don't know of a lot of premade options for this kind of amp, but perhaps one of these inline RF amp modules would qualify for being characterized and otherwise official.

Problem with these RF amps is they don't go down to DC and they are rather limited regarding the load impedance (usually 50 Ohms). If it's got to be something off-the-shelf, @HighVoltage's best chance are probably the mentioned Rigol power amp or it's Siglent counterpart SPA1010.

If a DIY solution would be an option, a single LT1210 will easily match the requirements. The difficulty with the high-power, parrallel solution that I'm conducting is that virtually all the components have to be matched (LT1210's for offset voltage, possibly for impedance at the feedback input and maybe also open loop gain, feedback resistors for very low deviation within one set so the gain of the ten paralleled amps is matched as accurate as possible). Only this way it is possible to use resistive summing up of the outputs (0.33 ohms in series with each output) without much cross currents. Supply voltage has to be very close to the limits for the device (it's planned to use +-17.5V) to reach the desired output voltage swing and it's got to be accurately regulated (probably a switcher with a linear post-regulator)

It seems the prototype performs quite well but the project has been on a hold for some time due to other duties. PSU design is a little awkward but I've got some ideas how to get where I want. Since it's a hobby project, something I always wanted to make, I'm not in a hurry and eventually it will be completed. So far, if I need to use the amp for some testing, I simply hook it up to a lab supply and strap it to a larger heat sink and that's it. And one can virtually fry anything attached to it...  :P
 

Offline capt bullshot

  • Super Contributor
  • ***
  • Posts: 3033
  • Country: de
    • Mostly useless stuff, but nice to have: wunderkis.de
Re: Amplifier for Function Generator needed (500 mA)
« Reply #12 on: September 24, 2018, 06:06:08 am »
There's some amplifiers by Toellner, e.g. the TOE 7607

https://www.toellner.de/amplifiers?pf=67&pi=70

And the TOE 7741 power function generator:
https://www.toellner.de/products?pf=61&pi=65

For homebrew stuff, I've made a simple amplifier using the ADA4870 chip.
Safety devices hinder evolution
 

Offline HighVoltageTopic starter

  • Super Contributor
  • ***
  • Posts: 5453
  • Country: de
Re: Amplifier for Function Generator needed (500 mA)
« Reply #13 on: September 25, 2018, 09:00:28 am »
Thank you all for the suggestions.
I most likely will order the RIGOL Amplifier for Euro 400 it seems reasonable and has good specs.

I came across another one that also has great specs, made by Clever Scope

Cleverscope CS1070
https://cleverscope.com/products/CS1070
-  0 - 52 MHz
-  1A output current on a 1 Ohm impedance
-  But the price of 1150 EURO seems steep


There are 3 kinds of people in this world, those who can count and those who can not.
 
The following users thanked this post: Wolfgang

Online tautech

  • Super Contributor
  • ***
  • Posts: 28136
  • Country: nz
  • Taupaki Technologies Ltd. Siglent Distributor NZ.
    • Taupaki Technologies Ltd.
Re: Amplifier for Function Generator needed (500 mA)
« Reply #14 on: September 25, 2018, 10:02:59 am »
Did you miss the mention of this one earlier by TurboTom:
https://store.siglentamerica.com/product/spa1010-10-watt-amplifier/

Seems a good bit cheaper.  :-//
Avid Rabid Hobbyist
Siglent Youtube channel: https://www.youtube.com/@SiglentVideo/videos
 

Offline HighVoltageTopic starter

  • Super Contributor
  • ***
  • Posts: 5453
  • Country: de
Re: Amplifier for Function Generator needed (500 mA)
« Reply #15 on: September 25, 2018, 10:07:18 am »
Ohh, thanks, I will have a closer look in to the Siglent SPA1010

Which one to trust more, Rigol or Siglent?




There are 3 kinds of people in this world, those who can count and those who can not.
 

Offline capt bullshot

  • Super Contributor
  • ***
  • Posts: 3033
  • Country: de
    • Mostly useless stuff, but nice to have: wunderkis.de
Re: Amplifier for Function Generator needed (500 mA)
« Reply #16 on: September 25, 2018, 10:13:52 am »
I came across another one that also has great specs, made by Clever Scope

Cleverscope CS1070


Interesting, looks like a box with the ADA4870 and some clever circuitry inside.
Safety devices hinder evolution
 

Online tautech

  • Super Contributor
  • ***
  • Posts: 28136
  • Country: nz
  • Taupaki Technologies Ltd. Siglent Distributor NZ.
    • Taupaki Technologies Ltd.
Re: Amplifier for Function Generator needed (500 mA)
« Reply #17 on: September 25, 2018, 10:18:50 am »
Ohh, thanks, I will have a closer look in to the Siglent SPA1010
I've never seen one or had one on my bench so I can only work from the specs and the manual that TurboTom has already linked.
You'll work it out to which is the best to suit your needs.  :)
Avid Rabid Hobbyist
Siglent Youtube channel: https://www.youtube.com/@SiglentVideo/videos
 

Offline HighVoltageTopic starter

  • Super Contributor
  • ***
  • Posts: 5453
  • Country: de
Re: Amplifier for Function Generator needed (500 mA)
« Reply #18 on: September 25, 2018, 10:32:31 am »
While searching for the Siglent SPA1010, I came across this:

Low Cost Function Generator Amplifier DIY
https://www.dmcinfo.com/latest-thinking/blog/id/9462/low-cost-function-generator-amplifier-diy
Based on the OPA541 Audio Amplifier
35 V and 10A
https://www.digikey.de/product-detail/en/texas-instruments/OPA541AP/OPA541AP-ND/251157


There are 3 kinds of people in this world, those who can count and those who can not.
 
The following users thanked this post: bdivi

Offline 21KUZY073

  • Contributor
  • Posts: 12
  • Country: se
Re: Amplifier for Function Generator needed (500 mA)
« Reply #19 on: December 16, 2022, 05:10:03 pm »
Did you test your amplifier? Bandwidth and so on... Have you some picture from oscilloscope?
 

Online BeBuLamar

  • Super Contributor
  • ***
  • Posts: 1137
  • Country: us
Re: Amplifier for Function Generator needed (500 mA)
« Reply #20 on: December 16, 2022, 06:25:58 pm »
Almost any audio amp circuit or buffer IC will do.

Building, or off-the-shelf, plug and go?

Tim

Audio amplifier can have bandwidth more than 20kHz but may not reach 100kHz without some loss.
 

Online Mechatrommer

  • Super Contributor
  • ***
  • Posts: 11535
  • Country: my
  • reassessing directives...
Re: Amplifier for Function Generator needed (500 mA)
« Reply #21 on: December 16, 2022, 07:35:36 pm »
Did you test your amplifier? Bandwidth and so on... Have you some picture from oscilloscope?
this is 4 years old thread... what took you so long to ask? today we have few $20 FG buffer from china that can go MHz. i recently built one using basic class AB amplifier that about 0.1dB flatness to 300kHz that i will later aim to be able to source/sink 5-10App current...
Nature: Evolution and the Illusion of Randomness (Stephen L. Talbott): Its now indisputable that... organisms “expertise” contextualizes its genome, and its nonsense to say that these powers are under the control of the genome being contextualized - Barbara McClintock
 

Online mawyatt

  • Super Contributor
  • ***
  • Posts: 3194
  • Country: us
Curiosity killed the cat, also depleted my wallet!
~Wyatt Labs by Mike~
 
The following users thanked this post: ledtester

Offline gamalot

  • Super Contributor
  • ***
  • Posts: 1300
  • Country: au
  • Correct my English
    • Youtube
Re: Amplifier for Function Generator needed (500 mA)
« Reply #23 on: December 17, 2022, 05:17:58 am »
This post reminds me that I have two OPA549M that I bought on ebay for 10AUD/pc about 5-7 years ago, maybe it's time to test if they are genuine.


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf