High-gain Differential Amplifier Research Articles

A silicon carbide high gain differential amplifier for extreme temperature applications

In this paper, a high temperature, high gain differential amplifier based on a custom-built silicon carbide (SiC) N-channel junction field effect transistor (JFET) only, without using complementary P-channel devices is proposed. The operation principle of this active load differential amplifier is discussed, and the expression of the differential gain is derived. A prototype circuit is fabricated using thick film process on an alumina substrate and tested from room temperature up to 500 °C to demonstrate the high temperature capability of the proposed differential amplifier. The differential gain of 50.8 dB is achieved with 58.6 dB common-mode rejection ratio (CMRR) and 9.1 MHz gain bandwidth product (GBW) at 500 °C. Excellent linearity and low output impedance of the proposed differential amplifier are also demonstrated at various temperatures. The proposed SiC JFET high gain differential amplifier can serve as a fundamental building block of the signal conditioning circuitry to be integrated with the sensing element for extreme environment applications.

Switched capacitor low‐pass filter with amorphous indium‐gallium‐zinc‐oxide thin‐film transistors on flexible substrate

This paper presents a novel switched capacitor biquad with a high gain differential amplifier for the first time using amorphous indium-gallium-zinc-oxide thin-film transistors on flexible (polyimide) substrate. The proposed low-pass filter was successfully characterised under normal ambient conditions. The circuit has shown a 3-dB cutoff frequency of 155 Hz and power consumption of 336 μW from measurements with a power supply voltage of 10 V. This circuit would find potential applications in wearable continuous health monitoring systems.

220–325-GHz 25-dB-Gain Differential Amplifier With High Common-Mode-Rejection Circuit in 60-nm InP-HEMT Technology

This letter presents a broadband and high-gain differential amplifier (DA) with a common-mode rejection circuit (CMRC) using 60-nm InP-HEMT technology. The differential pair in the DA is designed with common-source FET amplifiers. The CMRC implemented by short and open stubs with resistor degenerates the common-mode gain of the DA. Rat-race couplers (RRCs) are used as baluns for DA input and output. The fabricated DA chip exhibits superior gain and output power of 25 ± 3.5 dB and >3.5 dBm over the full WR3.4-band (220–325 GHz). Furthermore, the common-mode rejection is experimentally investigated using the common-mode test circuit of the DA. It is suggested that the fabricated DA chip has high common-mode rejection.

차동 저 잡음 증폭기의 입력 발룬 설계 최적화 기법

In this paper, the analysis of baluns that are inevitably required to design a differential low noise amplifier, The balun converts a single signal input from the antenna into a differential signal, which serves as an input to the differential amplifier. In addition, it protects the circuit from ESD(Electrostatic Discharge) coming through the antenna and helps with input matching. However, in the case of a passive balun used in general, since the AC signal is transmitted through electromagnetic coupling formed between two metal lines, it not only has loss without gain but also has the greatest influence on the total noise figure of the receiving end. Therefore, the design of a balun in a low-noise amplifier is very important, and it is important to design a balun in consideration of line width, line spacing, winding, radius, and layout symmetry that are necessary. In this paper, the factors to be considered for improving the quality factor of balun are summarized, and the tendency of variation of resistance, inductance, and capacitance of the balun according to design element change is analyzed. Based on the analysis results, it is proved that the design of input balun allows the design of low noise, high gain differential amplifier with gain of 24 dB and noise figure of 2.51 dB.

Design, fabrication and characterization of an x-ray bolometer for pulsed plasma x-ray sources

An x-ray bolometer for absolute measurement of broad-band soft x-ray fluence (10 eV < hν < 5 keV) from pulsed plasma sources is fabricated using an optical lithography technique. It is based on detecting the increase in resistance of a thin gold microstructure due to the temperature rise caused by absorption of x-ray energy in the absorber of the bolometer. The increase in the resistance is detected in a balanced bridge circuit and amplified by a low drift, high gain differential amplifier. The bolometer is calibrated for absolute sensitivity by comparing the signal of XUV pin diodes of known standard response detecting soft x-rays from a laser produced plasma. The response of the bolometer is measured to be ∼1.12 ± 0.05 mV mJ−1, with a heating time constant of 0.68 ms and a cooling time constant of 6 s. These values are found to be in good agreement with those derived using a simple analogy of charging of a capacitor by a pulsed signal. The details of bolometer design, fabrication and its characterization using x-rays (hν > 0.8 keV) from a copper plasma are presented.

Measurement and modelling of operational amplifier power supply rejection

A new approach to the measurement of operational amplifier power supply rejection, based on the measurement of the power supply injected signal gain of a high-gain differential amplifier configuration, is presented. Measured results for 741 and pin-compatible operational amplifiers are tabulated. A new SPICE macromodel which models operational amplifier power supply rejection characteristics is described. Design equations are provided to extract macromodel parameters from manufacturer's data sheets or measured power supply rejection data. Good agreement has been found between measured operational amplifier power supply rejection characteristics and simulated circuit performance based on the new macromodel.