A 5W ultra-broadband power amplifier using silicon LDMOSFETs

Abstract

We present the design of a high-efficiency power amplifier using silicon LDMOSFETs for the ultra-broadband from 2 to 500MHz. To achieve both the high efficiency and the output power required, the bias condition for the class-AB operation has been applied. In addition, a push-pull structure and a negative feedback network have been adopted for the broadband operation which has been implemented using broadband coaxial transmission line transformers and a broadband high-Q RF choke inductor. It is shown from the experimental results presented that the implemented power amplifier exhibits an output power at the 1dB compression point (P1dB) of more than 5W, as well as having a power-added efficiency of more than 43% at P1dB over the entire operational frequency band from 2 to 500MHz. The results also show very flat power gain characteristics of 22 1.5dB from 2MHz to 500MHz.Index Terms -Broadband power amplifier, broadband impedance transformer, coaxial transmission line, broadband RF choke, ferrite core

High bandwidth class B totem pole power amplifier for envelope modulators

“…The transformer coupled amplifier is usually adopted at high frequencies since it uses only N‐channel FETs or an NPN bipolar transistor. Although capable of multi‐decade operation [6] its bandwidth is limited by the input and output transformers, which are also physically large and expensive. The output transformer can be removed by stacking the transistors on top of one another in the totem pole configuration [7].…”

Design of a broadband power amplifier using an optimized feedback network

“…Broadband amplifiers generally utilize a feedback method to flatten their power gain response over a broad operating frequency band [2–12]. One of the most general ways of providing feedback is a shunt network, which senses the output voltage and supplies the feedback current to the input current.…”

“…As a specific instance, a typical shunt feedback network, consisting of an inductor ( L f ), a resistor ( R f ), and a capacitor ( C f ) in series, was selected for the simplicity of its circuit and capability to flatten the overall gain response over a wide frequency band [2–12]. The selected feedback network is applied to the open‐loop circuit of a gallium‐nitride high electron mobility transistor (GaN HEMT), as shown in Figure 1(b).…”

“…Broadband power amplifiers have been used in transmitters for military, medical, satellite, broadcasting, and instrumental applications [1–14]. Moreover, emerging broadband wireless communication systems, including various software‐defined or cognitive radio systems, require transmitters having a broader operational bandwidth.…”