Dear friends, I am working with stm32f103RBT6 MCU. I have used AMS1117 3.3V regulator both for MCU VDD and also for the VDDA pin. due to noise from GPRS device I need a way to reduce this noise. ADC value is affected about 2% of input value when GPRS is sending or connecting to server. I have a separate power switching regulator for GPRS and have used small signal capacitors as well as ferret beads. I think I should isolate MCU by a DC/DC from power source or use a reference voltage IC for AVDD. Is there any point other than these?
I thought most people had left carbon film resistors except for special applications, such as if you need high pulse stability.
Have a quick look at: www.resistorguide.com/.../
Your carbon film resistors aren't exactly at the top when it comes to stability. They age faster and are more affected by temperature than metal film or metal oxide resistors.
And for measurement instruments, there are even better choices available - such as metal foil resistors - even if lots of measurements don't need that quality level.
See also the table in this article: www.eetimes.com/document.asp
Thank you very much. Surely I have to change the resistor type. I find the right resistor by reviewing such differences.