Multiparallel Differential JFET Low-Noise Amplifier Circuit Based on Discrete Current Source

Yuqi Zhao, Tianyu Wang, Yang Zhang, Jun Lin

Abstract: Designing low-noise amplifier circuits is vital for the effective detection of weak signals. The parallel design of multiple junction field-effect transistors (JFETs) can effectively reduce the noise floor of the amplifier circuit. However, the process design and other factors mean that the current parameters of different JFET devices, even those of the same model, vary greatly, and this significant discretization leads to an uneven amplifier current and unreliable operation when multiple JFET devices are connected in parallel. To address this problem, this article proposes a multiparallel differential JFET low-noise amplification technique based on discrete current sources. This approach combines the characteristics of each JFET parameter with the design of a separate constant-current source to ensure that the current of each JFET branch can be controlled and adjusted to the optimal static operating point. The proposed device overcomes the problems caused by the discrete parameters of JFETs, which cannot work in parallel synchronously. We analyze the static operating point offset produced by the parameter discretization of JFETs and develop a multiparallel differential JFET low-noise amplifier circuit based on discrete current sources for testing. Experimental results show that the proposed circuit effectively eliminates the adverse effects of discretization and achieves very good noise performance in the low-frequency band. The multiparallel differential JFET low-noise amplification technique proposed in this article provides a new reference for the effective detection of weak signals.