A wide-band low noise L-band balanced transistor amplifier

Concurrent multiband low-noise amplifiers-theory, design, and applications

“…The bipolar junction transistor was the first solid-state active device to provide practical gain and NF at microwave frequencies [9]. In the seventies, breakthroughs in the development of field-effect transistors (FETs) (e.g., GaAs MESFET) led to higher gain and lower NF than bipolar transistors for the frequencies in the range of several gigahertz [10].…”

“…5 are (7) where (8) combining (6) and (7) results in the following expression for the noise factor : (9) where the second term is due to drain current noise, the third term is caused by gate-induced current noise, and the last term is the result of the correlation between the two noise sources (a similar correlation term exists between the collector and base shot noise of a bipolar transistor [50]). …”

“…Also, we can use the noise transformation of (24) to include the effect of an arbitrary gate series impedance . Under these assumptions, the coefficients in (7) will become (11) which can be used in (9) to estimate the NF of the LNA.…”

“…For smaller collector currents, the effect of base shot noise on the NF increases and the total NF degrades again. Third, a reduction in the collector current will lower the cutoff frequency 9 and, hence, increases the NF. As can be seen, this is similar to the well-known behavior of a single bipolar transistor amplifier where the reaches a minimum for a certain collector current [29].…”

Practical Limits in the Sensitivity-Linearity Trade-off for Radio Telescope Front Ends in the HF and VHF-low Bands

“…6; see e.g. Engelbrecht & Kurokawa (1965). This can be achieved by distributing power to the ampli¯er inputs using a passive hybrid with Fig.…”