本篇文章所介紹的負微分電阻元件(negative-differential-resistance；NDR)是利用3個HBT之元件所組成。而其電流-電壓特性曲線呈現N型，所以我們稱此架構為N型HBT-NDR元件。我們利用單穩態-雙穩態傳輸邏輯閘(monostable-bistable transition logic element，MOBILE)的操作原理將串聯的2個N型HBT-NDR元件分別當負載(LOAD)與驅動(DRIVER)，利用並聯在 NDR的金氧半場效電晶體(MOSFET)來調變其I-V特性曲線，來設計差動比較器電路(Defferent comparators)。
In this paper, a novel negative-differential-resistance (NDR) device composed of three heterojunction bipolar transistors (HBT) is investigated. Because the current - voltage (I-V) characteristic is N type, so we regard this NDR device as N-type HBT-NDR device. We use respectively two NDR devices as LOAD and DRIVER to design the logic circuit with the principle of monostable-bistable transition logic element (MOBILE). The I-V characteristic curves of NDR device can be modulated by a MOSFET which is connected parallel with the NDR device.