Design and parametric analysis of prototyped differential amplifier using double-gate mosfet.

Abstract

Differential Amplifiers (DA’s) are extensively utilized in a wide variety of electronic circuits, including operational amplifiers, instrumentation amplifiers, and Communication Systems (CS’s). They are typically built with BJTs and MOSFETs. Nevertheless, each type of transistor presents its own set of barriers when designing a DA. Amongst other challenges with BJTs is suffering from input base-emitter junctions with non-ideal input impedance. Decreased gain and loading effects may come from this. Due to the base-to-emitter voltage's dependence on temperature, they are susceptible to temperature changes, and they have a limited input voltage range, beyond which the transistors can be damaged. On the other side, Because of gate-source capacitance and gate leakage current, Single-Gate (SG) MOSFETs are more prone to noise; they suffer from Short Channel Effect (SCE) and have a limited input voltage range. The design process for a DA using a double gate MOSFET is presented in this work. The double gate MOSFET is a potential contender for use in analog circuit design because of its improved EC, low noise characteristics, reduced SCEs, and power consumption. The DA circuit proposed comprises two double-gate MOSFETs, BF998, constructed in a differential pair with a resistive load and a Constant Current Source (CCS). The proposed circuit is designed and simulated using a multism tool and was also constructed on Vero Board (VB). Various parameters are analysed on both simulated and practical circuits, such as differential output voltage gain, Common Mode Voltage Gain (CMVG), Common Mode Rejection Ratio (CMRR), Frequency Response (FR), and losses, to observe the performance of the proposed circuit. Simulated results for a differential voltage gain, common-mode gain, CMRR, and FR were obtained to be 24 dB, -224.22 dB, 246.86 dB, and 65 MHz, respectively. Practical results were obtained to be 24.44 dB, -73.81 dB, and 98.29 dB. A comparison has been made between the proposed circuit and the already existing designs, and the findings demonstrate that, when compared to traditional BJT and MOSFETbased DA’s, the presented DA using a double gate MOSFET offers considerable improvements in terms of differential voltage gain, cut-off frequency, CMRR, reduced SCEs, linearity, and noise performance. Therefore, based on these results, the designed DA is justified for use in operational amplifiers as input stage, RF, and other low-power electrical/electronic devices.