Function generator booster for MSO5000 - Page 1
Forum section: electronics / projects

author: thmjpr
author_rank: Regular Contributor
timestamp: March 11, 2020, 07:10:23 am
content: As mentioned in other threads, often the output voltage of built in waveform generators is lacking. In this case, MSO5000 output is +/-2.5V.This circuit is a simple plug-in board to provide a fixed output gain of 2x for both generator channels. So +/-5V output.The voltage rails are created from 5V USB byTPS65130.I've went with +/-7.5V for 3201 but up to +/-15V should be possible. The positive rail in that IC was rock solid, the negative rail however gives me some problems. With cf- removed it became stable, so far.USB output on the MSO5000 should be capable of at least 1A, could be up to 1.5A. But I did not test it with a load tester.Files:https://gitlab.com/thmjpr/fg_boost/Schematic:https://gitlab.com/thmjpr/fg_boost/-/raw/master/Rev1/rigol_fg_boost.pdfOpamp selection options:THS3091:- +/-15V- 210 MHz (G=2)- 250mATHS3095:- Same as 3091 with added power down pin and ref pin ( 8, 1)THS3061:- +/- 15V- 275MHz (G=2 MSOP)- 140mATHS3001:- +/- 16V- 350 MHz, 300MHz (G=2)- 120mATHS3201- +/- 7.5V supply- 850MHz at G=2 (Rf 768R)- 176mATHS3491:- +/- 15V- 900 MHz (G=5)- 420mAMost will have a thermal pad package for a slight increase in cost, it shouldn't be necessary when driving 50R load. But if you plan on abusing the output it would be good to have. Since the output bandwidth is not that high (25MHz), Rin could be some larger value to protect the AWG output should anything backfeed. Rt1 and Rt2 should be replaced with 1M, just to pull the input to Gnd when generator output is off.So far I have tried with THS3201, and will be getting MSOP THS3061 which may fit in the SOIC footprint..A few spare Rev1 boards will be available for sale at some point with THS3061.

author: schmitt trigger
author_rank: Super Contributor
timestamp: March 11, 2020, 02:11:49 pm
content: This is an interesting thread because I've an old HP sinewave generator which I cherish. However, it only has an output impedance of 600 ohm, and there have been instances where I require a lower impedance, at least 50 ohm.Of course in a sinewave generator, the THD levels are very important.Do you have an idea on the performance of your proposed circuit?

author: thmjpr
author_rank: Regular Contributor
timestamp: March 12, 2020, 06:33:47 am
content: SMA can be fitted as well for outputs:Quote from: schmitt trigger on March 11, 2020, 02:11:49 pmIn terms of bandwidth of the onboard generator, response is a flat from 0-25MHz.For higher frequencies.. its not terribly flat, I had a lot of peaking at ~450MHz. Could be excess capacitance on the PCB. But I think I'd need spec-an or similar for good HF measurements.For distortion, 2nd harmonic datasheet spec:THS3201 is -64 dBc at 10MHz RL=100R.THS3061 is -78 dBc at 10MHz RL=150R.Measuring on the scope I'm getting (THS3201):- 2nd harmonic -48dBc- 3rd harmonic -40dBcCompared to direct from the internal generator:- 2nd harmonic not visible- 3rd harmonic -58dBcSo there is a lot of distortion added, but I don't know specifically from where. I will compare to the THS3061 when I receive it.

author: schmitt trigger
author_rank: Super Contributor
timestamp: March 12, 2020, 04:27:45 pm
content: Thanks for sharing your findings.My generator only goes to 2 Mhz, so I should be ok.

author: oliv3r
author_rank: Frequent Contributor
timestamp: November 12, 2022, 10:52:26 am
content: Hey how is rev thmjpr comming along? Just curious of the status.

author: LinuxGuy123
author_rank: Regular Contributor
timestamp: January 23, 2025, 12:43:31 am
content: Was this ever tested with the THS3061 ?