Design of Ultra-Low Noise Preamplifier
Xiaofei Zhang · Dianzi qijian · 2008
A design of low noise preamplifier using discrete components for the low-impedance signal sources is specifically presented.According to series-wound amplifiers theory,the focus is to reduce the noise factor of the first transistor.The design makes the ultra-β PNP transistors work in the low Uce,low Ic1 micro-power state,and takes choice of low-noise measures such as resistive and capacitive components,and then the corresponding circuit is introduced.The test result indicates that the circuit's equivalent input noise voltage is 0.12 nV/Hz,which could be called ultra-low noise preamplifier.This circuit can be used in weak signal detection such as the locked-in amplifier,which needs high performance in noise characteristics.