IEEE Circuits and Systems Magazine - Q1 2020 - 13

of the best TIA topology for a certain application a challenging task.
In this regard, this paper presents a comparison between state of
the art, previously published TIA topologies. All topologies are simulated at four different simulation cases to account for various design
scenarios. The topologies are simulated with 10 pF photodiode (PD)
input capacitance and 5 KHz bandwidth (BW) while optimizing for
two different targets; one time for minimum input noise and the other
for minimum power consumption. Moreover, the same procedures
are performed with 2 pF PD and 100 MHz BW to account for higher
BW demanding applications. The studied topologies are compared
according to their transimpedance gain, power consumption, total
input referred noise current, and dynamic range (DR) to expose their
relative merits. A noise and a transimpedance gain mathematical
models are also presented for each topology to assist the comparison. Recommendations to designers on which TIA to select in a
certain application are concluded according to the obtained results.

I. Introduction
he rapid technological growth of CMOS bioelectronics integrated circuits have enhanced health care
in many different ways. Nowadays, optoelectronics
integrated circuits design is considered as one of the most
rapidly evolving research topics. Pulse oximetery is one of
the early methods emerged on the health care field that
uses optoelectronics integrated circuits, see Fig. 1. It uti-

lizes two wavelengths (IR and Red) to measure pulsating
arteries blood oxygen saturation [1]. Another revolutionary technique that relays on optoelectronics which is currently under developing and testing is the cuffless blood
pressure measurement using photoplethysmogram (PPG)
[2]-[4]. Fig. 2 shows a block diagram of a state of the art
handheld PPG based cuffless blood pressure device [5].

LCD

Post
Amplifier

Red
IR

Bi-Color
LED

Buffer

LED
Driver

SPI

Laptop

A /D
Converter

Amplitude
Calculation

Wrist

UART
-Rx
Wireless
Module

Wireless

Signal
Processing

BP Algorithm

UART
-Tx

Microprocessor

Dimming
Calculation

LED

PD
Multiplexer

Inversion
Pre-Amplifier

Band-Pass Filter

Vref

Display

Calibrate

Gain Adjusting
I -V

Calibration
Algorithm

SBP
DBP
HR

SPI

Vref

DAC

Light Adjusting

940 nm (IR)

Transimpedance
Amplifier

MCU

Figure 1. A block diagram of a typical pulse Oximeter device.

UART
-Rx

LED Driver

ADC

TIA

Vref

Programmable
Gain Amplifier

Commercial
Device

Vref

Regulator

Figure 2. A block diagram of a state of the art PPG blood pressure device [[5]].

Ahmed Atef is with the Electrical and Computer Engineering, Faculty of Applied Science, University of British Columbia, Canada (e-mail: ahmed@ece
.ubc.ca), Mohamed Atef is with the Electrical Engineering Dep., United Arab Emirates University, Abu Dhabi, and with the Electrical Engineering
Dep., Assiut University, Egypt (e-mail: moh_atef@aun.edu.eg), Elsayed Esam M. Khaled is with the Electrical Engineering Dep., Faculty of Engineering,
Assiut University, Egypt, and Dean; Higher Institute of Engineering and Technology, Sohag, Egypt (e-mail: esamk54_2000@aun.edu.eg), and Mohamed
Abbas is with the Electrical Engineering Dep., Faculty of Engineering, Assiut University, Egypt, and Electrical Engineering Dep., College of Engineering,
King Saud University, Saudi Arabia (e-mail: m-abbas@aun.edu.eg).
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