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How to Enlarge the Bandwidth Without Increasing the Noise in
OP-AMP-Based Transimpedance Amplifier
Team members:
Sembek Zaliyev,
Sholpan Zhylkaidarova
Course:
Integrated
Circuit Design
Instructor:
Alex James
Abstract
This poster illustrates the evaluation
of two methods of enlarging
bandwidth without increasing the
noise
in
op
amp
based
transimpedance amplifier
Introduction
The importance of the enlarging the
bandwidth in op amp is directly
connected with data transfer rate.
From most commonly
used circuit in figure
1,
the
frequency
response
of
a
transimpedance
Suggested Improvement:

High feedback resistor
amplifier is inversely
Figure 1. Commonly
proportional to the
used circuit [5]
gain set by the feedback resistor
1
𝑓𝑅 =
2𝜋𝑅𝑅 𝐶𝑅
From figure 2, the proposed new
topology circuit consist to 2 low
noise op amp OP27
Results
Methods/Design
Proposed two methods:
 Increase the feedback resistors
value
 Divide feedback resistor for N parts
in series connection
Figure 4. Obtained result of 1st method
Suggested Improvement:

High feedback resistor
Figure 2. Alternative new topology circuit
Results of 2nd method
 Increase in bandwidth 1.5 times
 Decrease in noise 5 times
Results
Results 1st method
 Significant decrease of noise
performance
Problem:
 Decrease in bandwidth
Figure 5. PSD noise result of 2nd method
Low noise
Low drift
High speed
Excellent CMRR
High open-loop
gain
80 nV p-p (0.1 Hz to 10
Hz), 3 nV/√Hz
0.2 μV/°C
2.8V/μs slew rate,8 MHz
gain bandwidth
126 dB at VCM of ±11 V
Problem:
 Insignificant increase in bandwidth
Modification:
1.8 million
Table 1. OP27 characteristics
Figure 3. PSD noise result of
1st
method
 Resistor with low parasitic effect
Discussion
Difference on results:
 Lower
increasing
factor
of
bandwidth than observed paper’s
results
Possible reasons:
 Chosen
type
of
operational
amplifier
 Simulator do not consider some
effect such as temperature
Conclusion/Recommendation
Further improvements:
 Choose proper operational amplifier
with low noise
 Consider temperature effect on
circuit
 Use better simulator software or test
on prototype
Two alternative circuit topologies are
investigated and simulated. First
circuit topology decreases the noise.
The second topology increases the
bandwidth. The main drawbacks of
circuit topologies proposed by
reference paper are indicated and
possible solutions are included.
Reference list
[1] C.Ciofi, F. Crupi, C. Pace and G.Scandurra “How to enlarge the bandwidth
without increasing the noise io op-amp-based transimpedance amplifier” IEEE
Transactions on Instrumentation and measurement, vol. 55, no. 3, June 2006.
[2] J. Karki, “Effect of parasitic capacitance in op amp circuit” Texas Instruments,
Dallas, Texas, September 2000.
(http://www.ti.com.cn/cn/lit/an/sloa013a/sloa013a.pdf)