An inductorless CMOS limiting amplifier with stream-mode active feedback

Abstract

We present an inductorless circuit technique for a CMOS limiting amplifier (LA), which consists of an input buffer, third-order broadband gain stages, and an output buffer for driving 50-Ω transmission lines. By employing stream-mode active feedback with negative capacitance circuit (NCC), the bandwidth of the proposed circuit can be effectively enhanced while maintaining a flat frequency response within the −3 dB bandwidth. Based on TSMC 0.18-µm CMOS process, the proposed LA circuit is optimized and implemented. The measurement results shown that the −3 dB bandwidth is 7.2 GHz with a voltage gain of 41 dB, and a data rate of 9 Gb/s is successfully achieved. The fluctuation of the group delay is less than ²25 ps, and the maximum output voltage is 1 V pp. The measured noise figure of the LA circuit is about 10 dB. Due to the absence of spiral inductors, the die only occupies a core size of 0.3 × 0.2 mm 2 , and consumes 79 mW from a 1.8 V supply voltage.

An energy- and area-efficient limiting amplifier with interleaving feedback for 25Gb/s optical receiver

“…To expand the LA bandwidth to support higher data transmission, active feedback technique, as an effective solution to improve the gain-bandwidth product, is commonly used in the design of LA. Non-interleaving feedback usually shifts the poles by adding a negative feedback between the paths, thus improving bandwidth, but it may cause large fluctuation of frequency response [18]. As an alternative solution, the interleaving feedback technique is adopted in this work to broaden the bandwidth and achieve flatness response.…”

“…As a result, various inductor-less bandwidth expansion techniques have been explored. Capacitive peaking, such as capacitance degeneration [16,17] and negative capacitance compensation [18,19], is a commonly used approach to enhance the bandwidth. Due to the high-pass characteristic of capacitive peaking technique, high-frequency noise will be introduced, which degrades the receiver's sensitivity.…”

“…Cherry-Hooper (CH) configuration [15,17,20] improves the bandwidth through resistance feedback, but it will consume more power than that of inductive or capacitive peaking, and the bandwidth will be deteriorated significantly when multi-stage CH is cascaded to provide appropriate gain. Recently, active feedback technique [18,21,22,23,24] is proposed for its remarkable bandwidth expansion effect. However, large fluctuation of the frequency response may be occurs, and there is large headroom to optimize the energy efficiency.…”