ABSTRACT
This chapter presents block diagrams of a feedback voltage amplifier, feedback current amplifier, feedback transconductance amplifier and a feedback transimpedance amplifier. Coupling amplifiers in series allows the circuit to increase its gain, either allowing impedance matching in the case of power amplifiers; or impedance mismatching in the case of signal amplifiers. Coupling also allows the circuit to compensate for the internal noise from the amplifiers, represented by its figure noise. Therefore, it suffices that the first amplifier has a low noise figure, in addition to a high gain, for the total noise figure to be practically the same as the first stage. This strategy is largely applied for the reception of satellite signals, which are very weak as they reach the Earth's surface. A Low Noise Amplifier is commonly found installed directly on the reception antenna.
