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parezj / EMBO

EMBO - Scope for only $6. Embedded instruments: Oscilloscope, Logic Analyzer, Voltmeter, Counter, PWM and Signal Generator on STM32 MCUs (F1, F3, L4, G4 ....). PC app for Windows, Ubuntu and macOS. Firmware is in C, PC GUI app is in C++ Qt 5.
https://embo.jakubparez.com
MIT License
144 stars 37 forks source link

stm32F303: opamp? #22

Closed msalat closed 4 months ago

msalat commented 4 months ago

Dear Mr. Pařez, are there plans to use the internal op amps of the stm32F303? I greped superficially through the sources and I'm not sure that they are in use. Perhaps it could improve input impedance. Kind regards, Jochen

msalat commented 4 months ago

Oh just looked at the characteristics of an TI OPA2340 I've used earlier: 10^13 Ohm, 6 pF input impedance. Perhaps not comparable to the stm32F303 internal opamp.

msalat commented 4 months ago

R_AIN_max is 0.82 kΩ @ 72 MHz, 4.5 sampling cycles, 8 bit ADC ≙ 5.5 MSPS.

The internal opamp has R_LOAD ≥ 4 kΩ .

If limited to 2.6 MSPS (19.5 sampling cycles, 8 bit ADC), R_AIN_max = 3.9 kΩ - that matches.