When amperometric biosensors drift, their sensitivity drops with time:
the same difference in detected concentration value ∆
C
results in lower sen-
sor output current ∆
I
as the measurement/monitoring time progresses. This
limitation affects the longevity of biosensors. To counterbalance for the drop
in sensitivity, manual adjustment of the I-to-V transimpedance gain is usually
applied. This paper presents an automatic transimpedance gain control cir-
cuit suitable for switched-capacitor-based current analogue front-ends. The
circuit has been fabricated in the 0.35
μm
AMS technology, occupies an area
of 0.028
mm
2
and consumes 14.5
μW
from a 3.3
V
supply. Measured results
confirm the automatic selection between three values of transimpedance gain,
namely 1,10 and 100
G
Ω each optimised for sensor current range values of
±
1.65
nA
,
±
165
pA
and
±
16.5
pA
respectively. Though the reported topology
has been tailored for glucose/lactate amperometric biosensors of slow tem-
poral dynamics, its parameters can be made to match the conditions of other
physiological/physical processes in need of monitoring.