Oscilloscope preamplifier and ADC

[simce]

oscilloscope adc

I want to design PIC based handheld digital storage oscilloscope with LCD display that can analyze frequencies from 0-5MHz, but I'm not sure what kind of preamplifier to use and what ADC should I use.
As I think preamplifier can be made with some operational amplifier but I don't know which one to use. I need suggestion and maybe any schematic and proposition for ADC that can sample with frequency of about 15-20MHz.

 

[oven]

oscilloscope preamp

Ti TLC5510 20Mhz 8byte TLC5540 40Mhz 8byte
The two High rate ADC is enough clock for 5Mhz Signal.
because you have to get a 10Mhz ADC for stabile
anti-overlap.
So, you must a Sram or Fifo for store ADC data.

Search in Internet, you can find some article.

Circuit Cellar magazine


That have many project.

 

[petarpav]

oscilloscope preamplifier

Hi, I think that PIC micro don't enought power to catch and display 5MHz signals.

Best regards.

 

[simce]

glcd high speed oscilloscope

I won't use pic to catch the info from ADC but as controll logic. Data from ADC will be transferred in to SRAM from where i'll transfer them on display via PIC.

 

[manitooo]

sram adc

If it's just a State machine you want to do with your PIC, try to use CPLD instead... (read from SRAM, Write to LCD)...

Moreover, the CPLD could be used to make clock divider so you could be able to control the sampling frequency.... and if you have a high Frequency to drive your CPLD, you will be able to divide it and shift it a multiple way that could be used to pipelined your sampling... then you could use low cost ADC running in pipeline... for a high speed measure ..

great isn't it ?

 

[simce]

adc oscilloscope

I suppose that CPLD, ASIC or similar products are more effective, but since i'm not exerienced in such technologies i'll use Microchip or Motorola MCU to make this transfer from ADC to SRAM, and than to Graphic LCD. ADC to SRAM transfer will be direct and then i'll use data from SRAM and display waveform on LCD.
I'll use external circuitry for clock and similar tasks. For me the only problem is analog part (preamplifier and such circuits).

 

[petarpav]

designing oscilloscope preamp

Hi, the fastest pic is 40MHz( 10MHz instruction cycle)
and max data sampling rate to sram will be about 500kHz-1MHz(max 2 MHz).....
And I thing you need PLD to catch data to sram, and pic only display it later.

Best regards.

 

[simce]

oscilliscope preamplifier

No, i don't need fast MCU, i can run mcu even at 4MHz, and i'll use external oscillation circuit to drive sram and adc. Additional address unit will drive SRAM during sample period. This circuit can run even on 60MHz or more. MCU will just trigger this circuit, transfer data from SRAM to LCD, make some calculations (FFT, Frequency calculation, RMS....). Also as you said PLD can be used, but i don't have development tools and knowledge how to implement this.
Also if any one is interested in such a project he is welcomed to join me in development of it. I think that this device won't cost more than 100-120 EUR in components.

 

[jzo777n]

oscilloscope preamplifier circuit

Take a look att Bitscope's preamplifier and ADC.
The schematic are avaliable at www.bitscope.com

 

[alphi]

adc circuits measuring with ossiloscope

Bitscope is very good,but tlc5540 is 40Mhz sample,it is waste.
you can use a lower sample 8 bit adc,and a -10(100ns) sram for it,and a xc9536 for memory tranfer engine.

 

[simce]

designing oscilloscope analog input

For now maybe 40MHz is waste, but maybe in near future i'll increase input bandwidth and than i won't need to look for another ADC.
Also this way i'll get 8 samples for 5MHz and i won't need any in depth DSP procesing of the signal.
I'm planing to use 256 or 512kB SRAM from Cypress as storage.

 

[monnoliv]

preamplifier oscilloscope wideband

Look here for an example of an analog input stage for your DSO: **broken link removed**.
I suggest you to use FET input op-amp.
bye,