A Low-Noise High-Gain Broadband Transformer-Based Inverter-Based Transimpedance Amplifier

Abstract

In this paper, a transformer-based bandwidth (BW) extension technique is employed to improve the BW, noise, and silicon area of inverter-based transimpedance amplifiers (TIAs) even when they use inductive peaking. A TIA based on the proposed technique, designed and laid out in a 16-nm FinFET process, demonstrates a 36% increased in BW, a 19% reduction in input-referred noise, and a 57% reduction in silicon area compared to the conventional TIA with inductive peaking. In the proposed TIA architecture, inclusion of a transformer in the forward path compensates partially for the parasitic capacitances of the inverter and relaxes the transimpedance limit of the conventional TIA. The proposed technique also lowers the input-referred current noise spectrum of the TIA. Post-layout in companion with electromagnetic (EM) simulations and statistical analysis are employed to verify the effectiveness of the proposed architecture. Simulation results show that the TIA achieves a transimpedance gain of 58 dB , a BW of 17.4 GHz, an input-referred noise of 17.4 pA/sqrt (Hz), and an eye-opening of 20 mV at a data-rate of 64 Gbps PAM4 and at a bit-error-rate (BER) of 1E-6. The whole TIA chain is expected to consume 19 mW and occupies an active area of 0.023 mm 2 . transimpedance amplifier, PAM4, statistical eyediagram. INDEX TERMS

An Inductorless Optical Receiver Front-End Employing a High Gain-BW Product Differential Transimpedance Amplifier in 16-nm FinFET Process

“…The noise of the inverter-based TIA is mainly dominated by the noise contribution of the transistor channel and the feedback resistor [10]. The noise of the feedback resistor directly contributes to the input noise [10].…”

“…The conventional inverter-based TIA [10] with a capacitive load and an electrical model of the PD is shown in Fig. 1(a).…”

“…In this regard, a TIA with a smaller input resistance is desired to achieve a wider bandwidth [9]. Moreover, the input-referred noise of the TIA directly affects the receiver bit-error-rate (BER) [10]. To lower the noise, larger devices should be utilized at the cost of larger parasitics, power consumption, and area.…”

“…Several inductive peaking techniques are reported, including series-inductive peaking (SIP) [3][4][10], shunt-inductive peaking (SHIP) [3][4][10], π-type inductive peaking (PIP) [6], and T-type inductive peaking (TIP) [7]. However, having inductors and transformers [10] in the design increases the silicon area, and impedes implementation in low-cost digital processes due to the lack of thick metal layers and high quality factor passive components [11]. Moreover, the coupling to the substrate increases through the inductors which results in higher An Inductorless Optical Receiver Front-End Employing a High Gain-BW Product Differential Transimpedance Amplifier in 16-nm FinFET Process crosstalk [11].…”

“…In the proposed TIA chain, the single-ended to differential block and the core TIA are combined into one block and differential signaling is utilized at the first stage of the receiver chain. Compared to [10], this work implements an inductorless optical receiver front-end including a novel fully-differential TIA (the TIA and single-ended to differential conversion are combined into one block) in companion with a negative capacitance generation circuit to improve the gain-BW product. The paper is organized as follows; Section II provides the background.…”