Measurement of operational amplifier voltage noise spectral density using FFT functions on CTS LCT40 low cost linear test system

• Main Author: Yujuico, Ronito Arcadio Briones
• Format: text
• Language: English
• Published: Animo Repository 2006
• Subjects: Amplifiers (Electronics)—Noise—Measurement; Electrical and Electronics; Systems and Communications
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/6772
• Institution: De La Salle University

Amplifier noise is an important parameter because it dictates the level of accuracy of any electronic system. This paper will discuss the method of measuring operational amplifier voltage noise spectral density using the low frequency digitizer, low pass filter and FFT (fast Fourier transform) functions of CTS (Component Test Systems) LCT40 low cost linear tester. Performance/DUT (Device Under Test) board was designed to have a high noise gain and low input noise so that quantization noise introduce by the low frequency digitizer and programmable gain amplifier input noise can be neglected with insignificant measurement error. The test program was written to check the Performance/DUT board noise gain accuracy before digitizing DUT noise and computing the rms (root-mean-square) average FFT from 64 individual FFTs. Low noise amplifiers OP37 and OP77 were tested on SRS (Stanford Research Systems) SR760 FFT spectrum analyzer to serve as the reference. Finally, CTS LCT40 10Hz and 1kHz voltage noise spectral density measurement were verified to be accurate within ±2% (±0.2dB) to the reference.