The noise performance of amplifier circuits is greatly affected by the Johnson noise of resistors—the source resistance and feedback resistors. Most everyone seems to know that resistors have noise but may be a bit foggy on some of the details. Here’s a bite-sized review in preparation for future discussions on amplifier noise:
Click Here to read on EDN magazine web site.
Table of Contents for all The Signal blogs, organized by topic.
If I take the result of the quiz right, doesn't it mean that the total open circuit noise voltage is independent of the resistor value and only the noise frequency bandwidth depends on the resistor value? You always have a stray parallel capacitance, even if it is infinite small?
Jens-Michael-- you are correct, assuming a constant stray capacitance, the total noise is independent of the resistor value. Higher value resistors have a higher noise density but the bandwidth rolls off at a lower frequency.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.