Input stages for amplifiers connected to very-low or very-high impedance signal sources

In this paper, the design of linear amplifiers for current sources with very low, or voltage sources with very high impedance is discussed. In designing negative-feedback amplifiers for these sources, the loopgain is often low as a result of the source impedance, thus making it difficult to obtain a sufficiently high bandwidth. Here, it is proposed to use CB or CC stages in front of a negative-feedback amplifier. It turns out that the use of these stages does not have to have large detrimental effects on noise or distortion properties, while providing a good means to achieve a higher bandwidth. Moreover, the system becomes more robust to source parameter variations. Keywords— linear amplifiers, bandwidth optimization, structured electronic design