basic circuit of a dso - Page 1
Forum section: electronics / beginners

author: abhimanyu
author_rank: Newbie
timestamp: August 26, 2010, 08:17:39 am
content: hii have some doubts about the circuit design of the ossiloscope shown in this videohttp://www.eevblog.com/2009/10/12/eevblog-37-rigol-ds1052e-oscilloscope-teardown/1.how do they change the analog input form channel 1 to 2or do they have the same circuit made for each channel2.how do they sample high voltages when their adc is capable of only 1v p-p

author: GeoffS
author_rank: Unknown
timestamp: August 26, 2010, 08:31:49 am
content: I think the only people who could tell you this for sure are Rigol and they're unlikely to reveal their design secrets

author: abhimanyu
author_rank: Newbie
timestamp: August 26, 2010, 08:40:14 am
content: @tumutboundi feel David would have surely looked into it when when he had opened that dso

author: Unknown
author_rank: Unknown
timestamp: August 26, 2010, 09:13:05 am
content: Quote from: abhimanyu on August 26, 2010, 08:17:39 amI'm sure both channels have separate analog front-ends, the ADCs from both channels can be combined for double the sample rate, they probably use some kind of analog switch.Quote from: abhimanyu on August 26, 2010, 08:17:39 amCompensated voltage dividers (parallel RC so the ratio of the impedance is constant, regardless of the frequency). They divide the voltage down within the range of the vertical amplifiers.Tektronix published a lot about oscilloscopes (search for the Concepts series), but this was way before the modern DSO. By the time the DSO came around, companies had stopped publishing detailed technical explanations. But apart from the digitizer/CRT, many parts are similar in DSOs and CROs.

author: EEVblog
author_rank: Unknown
timestamp: August 26, 2010, 11:47:28 am
content: Quote from: abhimanyu on August 26, 2010, 08:17:39 am1. It's done in software and hardware multiplexing. The input signal can be switched through to either 1 or 2 ADC channels depending on the speed required. Both channles can be sampled at once, and the software can simply ignore one channel.2. That's the function of the "analog front end" or "vertical amplifier/attenuator" (the bit inside the metal can). Every oscilloscope has one, it is designed to scale the input to the 1V range of the ADC. It is done with a software programmable gain amplifier and/or attenuator.Dave.

author: Simon
author_rank: Unknown
timestamp: August 26, 2010, 11:55:48 am
content: if your trying to say it can't work your a bit late, we all use them and have had no problems

author: abhimanyu
author_rank: Newbie
timestamp: August 26, 2010, 04:46:33 pm
content: okkSo in a 1Ghz sampling rate dso when we are using both the channels actually the sampling rate of each channel is 500Mhz which makes it a total of 1Ghzhope I got it right!!!

author: Unknown
author_rank: Unknown
timestamp: August 26, 2010, 05:00:05 pm
content: Yep, and each channel consists of a bunch of ADCs (5?), all interleaved.

author: Simon
author_rank: Unknown
timestamp: August 26, 2010, 05:14:21 pm
content: no each channel is multiplexed into a set of 5 chips that have 2 AD's each, if you watch daves review of it it's all explained, the chips are 2 X 40 MHz ADC's that have been overclocked to 100 MHz X 2 per IC X 5 IC's = 1000 MHz = 1GHz interleaved

author: abhimanyu
author_rank: Newbie
timestamp: August 27, 2010, 04:19:05 pm
content: @allthank youthis information was very useful..thanx once again