## 3 Memristive Analog Design
### Memristive RF Circuits
#### 3.2.3 CMOS Amplifier  
The growing demand for multi-band and multi-standard wireless devices requires flexible designs that can support multiple frequency bands and communication protocols in a single device, such as Wi-Fi, Bluetooth, and cellular. In [51], a low-voltage high-gain wideband three-stage true-class AB amplifier is presented. The schematic of the proposed amplifier is depicted in Figure 6a[51] and designed using a 0.18 \(\upmu\)m CMOS process. As shown in Figure 6b[51], the amplifier achieves a tunable high gain and operates at a low supply voltage of 1.8 V, making it suitable for low-power applications. The memristor-based pole-zero cancellation improves the amplifier's performance in terms of linearity and distortion, while the nested Miller compensation technique helps to make it more stable and widen its bandwidth. The amplifier's gain and phase margin are crucial for ensuring stability and performance across various load conditions. By analyzing the amplifier's response to these different loads, engineers can optimize its design for maximum efficiency and reliability. The proposed amplifier operates with a \(\pm\)1 V supply voltage and 175 \(\upmu\)A bias current, which is capable of driving a wide range of loads and maintaining a phase margin of over 60\({}^{\circ}\). Its unity gain frequency is 136.7 MHz, offering a high bandwidth without affecting the amplifier gain. Also, the simulation results show that the proposed amplifier is designed to handle a variety of load configurations to ensure optimal performance in different scenarios (200 pF//1 M\(\Omega\), 100 pF//10 K\(\Omega\), and 25 pF//1 K\(\Omega\)), as depicted in Figure 6b[51]. The amplifier's gain ranges from 70.5 dB to 92 dB. This flexibility allows for versatility in applications requiring varying impedance levels. Overall, this amplifier is designed to provide high performance and versatility in various applications. With its wide load-driving capability and excellent phase margin, it ensures stable and reliable operation even with demanding loads. Additionally, the high unity gain frequency allowsfor accurate signal reproduction and fast response times, making it suitable for applications requiring a high bandwidth. A dual-band memristor-based Low-Noise Amplifier (LNA) is introduced in [52]. The proposed dual-band source-degenerated CS LNA implementation employs TIME inductors [49] as the gate and output inductors. TIME inductors allow for gain and frequency tunability, enhancing signal reception in the 2.4 GHz and 5 GHz WiFi bands. The LNA enhances signal reception in both frequency bands by providing high gain and low noise figures. The simulation results demonstrate that the LNA has a small area overhead and achieves high gains of 18.8 dB and 10.3 dB at 2.4 GHz and 5 GHz, respectively, while maintaining a low noise figure below 2.3 dB. An optimized hybrid Operational Transconductance Amplifier (OTA) using source degeneration with adaptive biasing for high-frequency applications is presented in [53]. The proposed OTA design combines the benefits of source degeneration and adaptive biasing techniques to enhance its performance in high-frequency applications. The integration of these techniques results in improved linearity, reduced power consumption, a reduced die area, and enhanced stability, making it an ideal choice for demanding high-frequency circuits. The circuit operates with a supply voltage of \(\pm\)1 V and a bias current. The linearity of the OTA is improved using memristor, which provides nonlinear behavior that can be adjusted to compensate for the nonlinearity inherent in the OTA itself. This allows for better accuracy and fidelity in high-frequency signal amplification, making it suitable for applications such as wireless communication or audio processing. Additionally, the use of a memristor also contributes to lower power consumption and the improved overall efficiency of the circuit.