CMOS Front Ends for Millimeter Wave Wireless Communication Systems by Noël Deferm & Patrick Reynaert

Author:Noël Deferm & Patrick Reynaert
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

4.1 Optimization for Gain: Small-Signal Amplifiers

As already mentioned, the low available gain of the nMOS transistors makes the maximization of power gain one of the prior concerns in the design of a mm-wave amplifier. To maximize the overall gain of the amplifier, impedance matching networks have to be designed at the input and output of each transistor. This optimization process is not straightforward as a normal nMOS device is typically conditionally stable at mm-wave frequencies. This means the device can show potential unstable behavior. Moreover, the load impedance affects the input impedance and the source impedance affects the output impedance of the device, making the design procedure of matching networks not straightforward. However, in Chap. 2, a neutralization technique was discussed to reduce the feedback in the MOSFET. This significantly facilitates the analysis and the design of the transistor matching networks. Next to the stabilization of the transistor, this is one of the great advantages of the capacitive neutralization technique . The same analysis can be applied to cascode structures, provided that the cascode amplifier is also operating in the unconditionally stable region.

Fig. 4.1Unilateral transistor matching network diagram

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