Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Noise-Optimized Silicon Radiometers



George P. Eppeldauer


Transimpedance-gain, loop-gain, and voltage-gain requirements of photodide short-circuit-current meters are summarized for ac and dc optical radiation measurements. Design considerations to implement the gain equations in silicon radiometers are discussed. Silicon radiometers with improved dynamic characteristics were built, and tested. the frequency dependent photocurrent gains were measured and th noise performance was tested. the noise floor was optimized in ac measurement mode using photodides of different shunt resistance and operational amplifiers with low 1/f voltage and current noise. In dark (without any signal), the noise floor of the optimized radiometers was dominated by the resistor noise of the source resistance. The resistor noise was decreased and equalized to the amplified 1/f input noise at 9 Hz chop frequency and 30 s integration time constant, resulting in an equivalent photocurrent noise of 8 x 10-17 Arms. The lowest noise floor of 5 x 10-17 Arms was obtained at 100 s ontegration time constant. The silicon radiometers, optimized for ac measurements modes were compared. In ac mode, ten times shorter (40 s) overall measurement time was needed than in dc mode (400 s) to obtain the same 10-16 Arms noise floor.
Journal of Research (NIST JRES) -
105 No. 2


gain, noise, photocurrent, radiometer, sensitivity, silicon photodiodes


Eppeldauer, G. (2000), Noise-Optimized Silicon Radiometers, Journal of Research (NIST JRES), National Institute of Standards and Technology, Gaithersburg, MD (Accessed June 23, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created March 1, 2000, Updated June 2, 2021