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Analog Circuit Cells
Published in Wai-Kai Chen, Analog and VLSI Circuits, 2018
Kenneth V. Noren, John Choma, J. Trujillo, David G. Haigh, Bill Redman-White, Rahim Akbari-Dilmaghani, Mohammed Ismail, Shu-Chuan Huang, Chung-Chih Hung, Trond Saether
The amplifier circuits discussed previously are of the single-ended type. A single-ended amplifier has both input and output voltage signals referred to ground. In most IC applications, a differential amplifier is utilized. In this case, the amplifier has a differential input and may also have a differential output, in which case it is called a fully differential amplifier. It is usually easy and straightforward to convert singleended amplifiers to differential architectures.
CMOS Amplifiers
Published in Tertulien Ndjountche, CMOS Analog Integrated Circuits, 2017
The symbol of a fully differential amplifier is shown in Figure 5.8(c). For simplification, the V0CM node is generally omitted. A fully differential amplifier has the advantage over its single-ended counterpart of rejecting the common-mode noise. It should also be noted that even-order nonlinearities are canceled at the outputs of a differential circuit that is balanced or whose both sides are electrically similar and symmetrical with respect to the ground.
Single-ended amplifier-based touch readout circuit with immunity to display noise
Published in Journal of Information Display, 2023
The touch readout circuit, which reads out the touch signal from the capacitive touch panel, must be robust to display noise, because large display noise is injected from the operating display panel [1–7]. In particular, as the add-on type touch panel has advanced into an on-cell and further, an in-cell type touch panel, the gap between the display panel and the touch panel has been greatly decreased, and the display noise injected into the touch panel has become a more serious problem [3–10]. As shown in Figure 1, display noise is injected to the RX electrode of the touch panel through the common electrode located at the top of the display panel (for example, the cathode electrode in a top-emission OLED panel). Therefore, display noise is considered a common noise independent of the position in the panel [1,3–5,8,11,12]. Therefore, the display noise can be effectively suppressed by using a differential sensing method [1–3,6,11–13]. There are two common circuit implementations to realize the differential sensing method. One is to additionally use a fully differential amplifier that receives the outputs of the pair of readout amplifiers of two adjacent channels as differential inputs [6,12]. However, the added circuits increase the power consumption and the circuit area. The other is to design each channel’s readout amplifier as a fully differential amplifier [1–3,11,13]. This circuit, however, can only detect the difference in capacitance between the adjacent two channels, then it is not sufficient for touch detection. To determine a touch, an additional dummy RX line is needed as the reference for the touch panel.
Low-power fully monolithic MICS band receiver for 402-405 MHz implantable devices
Published in International Journal of Electronics, 2020
VGA is required to adjust the amplitude of the received signal and maximise the dynamic range of the overall receiver system. Settling time specifications usually require the variable gain stages in the receiver to have a dB-linear gain variation with control voltages. As shown in Figure 11, VGA circuits with a fully differential amplifier topology is used. The gain is varied through a 3-bit tuning resistor (R1, R2, R3) at the amplifier input, each of them is controlled by a digital bit b0 – b2 that enables/disables the resistor to be connected to a feedback resistance Rf through a transmission gate. The combination of Rf and the tuning resistors represents a feedback configuration between VGA output and input to control its transconductance gm. By changing the control bits b0-b2, the input resistance to the differential amplifier is varied such that gm changes. The use of gm-boosting results in increasing the effective transconductance of the differential pair, providing a high gain and minimising the gain error caused by gm variations. The input differential pair of the designed circuit achieves an improvement in the input range minimising the gain error caused by gm variations. A common-mode feedback block – not shown in figure – is used to control the common-mode signal for maximum output swing. The transmission gates at the input of the Amp has W/L ratios 9µm/0.12µm for PMOS and 4.5µm/0.12µm for NMOS while the amplifier core has W/L ratios 8.5µm/0.12µm for NMOS and 16µm/0.12µm for PMOS. The VGA achieves an approximately linear tuning range of 35 dB at a current consumption of 80 μA.
A 1.2V 0.2mW 27MHz CMOS limiting amplifier using cross-coupled active load structure
Published in Australian Journal of Electrical and Electronics Engineering, 2020
M. Saddam Hossain Khan, Surajit Das Barman, Ahmed Wasif Reza
Figure 2 depicts the schematic of the proposed LiA used for the single-stage which embodies a differential circuit with gain enhancement technique using cross-coupled structure for active load. A CMOS fully differential amplifier circuit is used where the low frequency gain or DC gain of the circuit depends on the output resistance of both PMOS and NMOS transistors. The inputs are given to the NMOS differential pair and the amplified differential output will be taken from the drain terminal of NMOS differential pair. A biasing voltage from the external biasing network is provided to supply a constant current in the tail for circuit operation (Amourah and Geiger 2001).