RF Amplifiers

RF amplifiers are electronic devices that accept a varying input signal and produce an output signal that varies in the same way as the input, but that has larger amplitude. RF amplifiers generate a completely new output signal based on the input, which may be voltage, current, or another type of signal. Usually, the input and output signals are of the same type; however, separate circuits are used. The input circuit applies varying resistance to an output circuit generated by the power supply, which smoothes the current to generate an even, uninterrupted signal. Depending on load of the output circuit, one or more RF pre-amplifiers may boost the signal and send the stronger output to a RF power amplifier (PA). Other types of RF amplifiers include low noise, pulse, bi-directional, multi-carrier, buffer, and limiting amplifiers. Detector log video amplifiers (DLVAs) are used to amplify or measure signals with a wide dynamic range and wide broadband. Successive detection log video amplifiers (SDLVAs) are log amplifiers that can operate over a wider dynamic range than DLVAs, while extended range detector log video amplifiers (ERDLVAs) are DLVAs that can operate with a wider operating frequency. 

Selecting RF amplifiers requires an analysis of several performance specifications.  Operating frequency is the frequency range for which RF amplifiers meet all guaranteed specifications. Design gain, the ratio of the output to the input power, is normally expressed in decibels (dB), or G_db = 10 * log (P_o/P_i). Output power is the signal power at the output of the amplifier under specified conditions such as temperature, load, voltage standing wave ratio (VSWR), and supply voltage. Gain flatness indicates the degree of the gain variation over its range of operating wavelengths.  Secondary performance specifications to consider include noise figure (NF), input VSWR, output VSWR, and monolithic microwave integrated circuit (MMIC) technology. The noise figure, a measure of the amount of noise added to the signal during normal operation, is the ratio of the signal-to-noise ratio at the input of the component and the signal-to-noise ratio measured at the output. The NF value sets the lower limit of the dynamic range of the amplifier. Input VSWR and output VSWR are unit-less ratios ranging from 1 to infinity that express the amount of reflected energy. 

There are several physical and electrical specifications to consider when selecting RF amplifiers. Physical specifications include package type and connector type. Package types include surface mount technology (SMT), flat pack, and through hole technology (THT). RF amplifiers may also be connectorized or use waveguide assemblies. Connector types include BNC, MCX, Mini UHF, MMCX, SMA, SMB, SMP, TNC, Type F, Type N, UHF, 1.6 / 5.6, and 7/16. Important electrical characteristics include nominal operating voltage and nominal impedance. Operating temperature is an important environmental parameter to consider.

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Part Numbers for RF Amplifiers