中圖分類號：TN402 文獻(xiàn)標(biāo)志碼：A DOI: 10.16157/j.issn.0258-7998.245990 中文引用格式： 鄧新偉，楊尚爭，毛佳烽，等. 一種應(yīng)用乒乓自歸零的高精度放大器[J]. 電子技術(shù)應(yīng)用，2025，51(3)：49-53. 英文引用格式： Deng Xinwei，Yang Shangzheng，Mao Jiafeng，et al. A high-precision amplifier using ping-pong auto-zeroing[J]. Application of Electronic Technique，2025，51(3)：49-53.
A high-precision amplifier using ping-pong auto-zeroing
Deng Xinwei，Yang Shangzheng，Mao Jiafeng，Hu Weibo，Ren Liru
College of Electronic Information and Optical Engineering， Nankai University
Abstract： This paper presents the design and implementation of a low-offset, high-gain operational amplifier (op-amp). The overall circuit consists of a bandgap reference, oscillator, frequency divider, auxiliary op-amp, and main op-amp. By employing a ping-pong auto-zeroing architecture, the circuit achieves continuous operation while significantly reducing the input offset voltage of the amplifier. Furthermore, this paper proposes a novel and efficient control timing scheme that effectively reduces the settling time during ping-pong switching at a relatively low cost, further minimizing the output glitches of the amplifier. The amplifier chip was designed and fabricated in a 350 nm CMOS process. Measurement results demonstrate that under a 5 V supply voltage, the amplifier consumes 0.65 mA current, achieves a maximum input offset voltage of 3 µV, provides a gain-bandwidth product of 8 MHz, and exhibits a noise spectral density as low as 30 nV/√Hz.
Key words : low-offset；ping-pong；auto-zeroing；amplifier
引言
隨著互補(bǔ)金屬氧化物半導(dǎo)體（Complementary Metal Oxide Semiconductor, CMOS）工藝的不斷發(fā)展，CMOS憑借其便于集成以及成本低等優(yōu)點(diǎn)，逐漸成為了主流工藝。但是CMOS放大器受失調(diào)電壓（1~10 mV）、溫漂以及1/f噪聲的影響，無法滿足高精度應(yīng)用的要求。通常在電路設(shè)計(jì)上解決上述問題有兩種技術(shù)：斬波技術(shù)和自歸零技術(shù)[1-2]。采用斬波技術(shù)會(huì)在放大器的輸出端引入紋波，如果放大器后面驅(qū)動(dòng)模數(shù)轉(zhuǎn)換器(ADC)，這種紋波在ADC采樣時(shí)會(huì)產(chǎn)生較大的誤差，除非采樣和斬波同步發(fā)生在紋波的過零點(diǎn)[3]。隨著斬波技術(shù)的發(fā)展，文獻(xiàn)[4-7]分別展示了不同的方法來減小紋波。但所有這些方法有一個(gè)共同的缺點(diǎn):當(dāng)輸入被調(diào)制時(shí)，即使放大器是無失調(diào)偏移的，它們有限的帶寬也將引起切換瞬變，而在放大器的輸出處解調(diào)時(shí)，切換瞬變會(huì)變成毛刺。而自歸零相比斬波而言，由于沒有調(diào)制解調(diào)過程，不會(huì)產(chǎn)生紋波[8]。但由于采樣作用，自歸零是一種不適用于連續(xù)時(shí)間工作的技術(shù)。當(dāng)需要連續(xù)時(shí)間操作時(shí)，則需要使用乒乓結(jié)構(gòu)[9]，其中兩個(gè)自歸零放大器彼此并聯(lián)運(yùn)行，一個(gè)自動(dòng)調(diào)零，一個(gè)用于放大信號。此外放大器在乒乓切換過程中，一般采用兩相非交疊時(shí)鐘控制切換時(shí)序[10]，但這樣會(huì)在放大器的輸出引入毛刺。
