Some Design Considerations for High-Frequency Transistor Amplifiers

Abstract

The major problem in the design of high‐frequency transistor amplifiers is the interaction between the output and the input of the amplifier caused by the internal feedback of the transistor. This problem is illustrated and the two common design approaches to a solution of the problem are discussed. Nyquist's criterion of stability and Bode's feedback theory are then used to obtain an engineering evaluation of the relative merits of these two design approaches from a stability standpoint. The positive nature of the internal transistor feedback is established in this stability evaluation. Finally, Bode's feedback theory is used to consider the relative merits of some of the broad banding techniques used in transistor video amplifier design. The over‐all analysis shows that many of the most practical and stable linear transistor amplifiers are very simple and can be built with a minimum of design effort.

A 219-µW ultra-low power low-noise amplifier for IEEE 802.15.4 based battery powered, portable, wearable IoT applications

“…The difference between the input signal ( V in ) and the feedback signal is the error signal ( V e ). The characteristics of positive feedback in circuits and its subsequent effect on impedance and gain has been reported in [22][23][24][25][26]. In Fig.…”

“…Therefore, the equations for voltage gain, NF and IIP3 derived in (5), (12) and (23) are now functions of SCE. Due to the complexity of the equations, analysis and design of the LNA (25) g m = WC ox v sat (26) [14] Resistive-feedback 1 + A v [15] Dual negative feedback 1 + A v [16] Local feedback 1 + A v [17] Negative feedback 1 + A v [18] Positive feedback 1 + A v [18] Double feedback x 1 + A v [20] Dual capacitor cross-coupled feedback with negative impedance [21] Active-feedback using complementary source follower (CSF)…”