BiCMOS variable gain transimpedance amplifier for automotive applications

Abstract

A new BiCMOS variable gain transimpedance amplifier with a large area integrated photodiode for automotive applications is presented. Through careful control of the input pole position and the frequency response of the core amplifier, the bandwidth of the transimpedance amplifier varies from 112 to 300 MHz when its gain changes from 14.2 kV to 400 V. The proposed circuit configuration maintains a high voltage across a common anode photodiode, and its bandwidth in highest gain varies from 121 to 102 MHz over a temperature range of 240 to þ1408C. Simulation results in a 0.6 mm Si BiCMOS technology are given. The amplifier consumes 16 mW from a 3.3 V supply.Introduction: Optical transmission technology is increasingly used in cars as an alternative for copper-based solutions [1]. Optical receivers for automotive communication networks must cope with a high ambient temperature range (240 to þ1258C), be cost-effective and low power. Cost-effectiveness implies usage of an integrated photodiode (PD) with large diameter (430 mm in this Letter) to relax the mechanical alignment accuracy requirement, resulting in a high PD capacitance of 4.8 pF. PDs can be made using the p-substrate as an anode and an n þ contact as a cathode [2]. To ensure a fast PD and minimise its capacitance, its reverse bias must be high. This is challenging at a supply voltage of 3.3 V. Variable gain transimpedance amplifiers (TIAs) are needed to ensure high dynamic range. In [3], a variable gain TIA is realised by splitting the core amplifier into two parallel amplifiers and adding their outputs together in a weighted sum fashion. Variable gain was realised by adjusting the weighting factor. However, owing to the varying open-loop gain it is difficult to control the bandwidth and peaking of the frequency response. In [4][5][6], current switches at the input of the TIA are used to steer part of the photodiode current away from the TIA for high optical input power. However, the voltage drop across the current switches results in low bias voltage across a common anode PD. In [7], a Darlington input stage is combined with MOSFETs used as voltage-controlled resistors to achieve wide dynamic range. However, the Darlington input stage is not suitable for a supply voltage of 3.3 V, and the use of ten MOSFETs to control the gain and frequency response makes the circuit design over a wide temperature range difficult. In this Letter we propose a new circuit that overcomes these disadvantages, and can handle a junction temperature range of 240 to þ1408C.

An integrated optical receiver for multilevel data communication over large core step index plastic optical fiber

“…Another receiver presented in [7] with an AGC-TIA and two integrated 430 lm diameter PDs had an estimated sensitivity of -28 dBm at a BER of 10 -9 using a binary signal at a DR of 150 Mbit/s [7]. Our presented receiver shows a better measured sensitivity (3 dB improvement) at nearly the double data rate.…”

An optical receiver for eight-level data communication over step index plastic optical fiber

“…Another receiver presented in [5] with AGC-TIA and two integrated 430 lm diameter PDs had an estimated sensitivity of À28 dBm at 10 À9 BER using a binary signal at a DR of 150 Mbit/s [5]. Our presented receiver shows a better measured sensitivity (3 dB improvement) at a 1.6 times higher data rate.…”

Design and simulation of differential transimpedance amplifier with active feedback for optical receivers

“…A direct trade‐off exists between the bandwidth and the input‐referred noise. Decreasing $${R}_{fb}$$ requires $${a}_{0}$$ to be increased proportionally and this is limited due to stability concerns 11 . Due to this, a trade‐off exists between gain, bandwidth, and input‐referred noise.…”

“…Using inductive peaking techniques, high speed is achieved at the cost and power 4 . Various inductorless TIA topologies proposed are available in the literature 2–16 . Some of them to mention are regulated cascode circuit based TIAs 2,6–9 and inverter based TIA 3 .…”