TS1001
The circuit in Figure 1 illustrates a typical
implementation used to amplify the output of an
oxygen detector. The TS1001 makes an
excellent choice for this application as it only draws
way to achieve this objective is to use an RC filter at
the noninverting terminal of the TS1001.
If additional attenuation is needed, a two-pole
Sallen-Key filter can be used to provide the
additional attenuation as shown in Figure 3.
Figure 3:
A Nanopower 2-Pole Sallen-Key Low-Pass Filter.
Figure 1:
A Nanopower, Precision Oxygen Gas Sensor
Amplifier.
0.6µA of supply current and operates on supply
voltages down to 0.65V. With the components
shown in the figure, the circuit consumes less than
0.7
μA
of supply current ensuring that small form-
factor single- or button-cell batteries (exhibiting low
mAh charge ratings) could last beyond the operating
life of the oxygen sensor. The precision
specifications of the TS1001, such as its low offset
voltage, low TCV
OS
, low input bias current, high
CMRR, and high PSRR are other factors which
make the TS1001 an excellent choice for this
application. Since oxygen sensors typically exhibit
an operating life of one to two years, an oxygen
sensor amplifier built around a TS1001 can operate
from a conventionally-available single 1.5-V alkaline
AA battery for over 290 years! At such low power
consumption from a single cell, the oxygen sensor
could be replaced over 150 times before the battery
requires replacing!
NanoWatt, Buffered Single-pole Low-Pass Filters
When receiving low-level signals, limiting the
bandwidth of the incoming signals into the system is
often required. As shown in Figure 2, the simplest
For best results, the filter’s cutoff frequency should
be 8 to 10 times lower than the TS1001’s crossover
frequency. Additional operational amplifier phase
margin shift can be avoided if the amplifier
bandwidth-to-signal bandwidth ratio is greater than
8.
The design equations for the 2-pole Sallen-Key low-
pass filter are given below with component values
selected to set a 400Hz low-pass filter cutoff
frequency:
R1 = R2 = R = 1MΩ
C1 = C2 = C = 400pF
Q = Filter Peaking Factor = 1
f–3dB = 1/(2 x
π
x RC) = 400 Hz
R3 = R4/(2-1/Q); with Q = 1, R3 = R4.
A Single +1.5 V Supply, Two Op Amp
Instrumentation Amplifier
The TS1001’s ultra-low supply current and ultra-low
voltage operation make it ideal for battery-powered
applications such as the instrumentation amplifier
shown in Figure 4.
Figure 4:
A Two Op Amp Instrumentation Amplifier.
Figure 2:
A Simple, Single-pole Active Low-Pass Filter.
The circuit utilizes the classic two op amp
instrumentation amplifier topology with four resistors
TS1001DS r1p0
RTFDS
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