Abstract: Considering the features of modern pre-amplifier circuit configurations, several misunderstandings and countermeasures in preamplifier design for sensor signal conditioning are studied. The results indicated that sometimes minimizing noise factor can't optimize the noise performance sometimes.RFI rectification errors are important error sources and to be often ignored, driving capacitive loads is common and oscillation problem often occurs, and using a single decoupling capacitor isn't an effective way to decoupling ICs at high power noise (ripple) frequencies. The solutions to these problems are proposed.