TS1001

TS1001 Rev. 1.0

Page 7

PIN FUNCTIONS

Pin

Label

Function

1

OUT

Amplifier Output.

2

Negative Supply or Analog GND. If applying a negative voltage to

this pin, connect a 0.1µF capacitor from this pin to analog GND.

3

+IN

Amplifier Non-inverting Input.

4

-IN

Amplifier Inverting Input.

5

Positive Supply Connection. Connect a 0.1µF bypass capacitor

from this pin to analog GND.

THEORY OF OPERATION

The TS1001 is fully functional for an input signal

differential amplifiers, a p-channel CMOS stage and

an n-channel CMOS stage that are active over

different ranges of the input common mode voltage.

The p-channel input pair is active for input common

to approximately 0.4V below the positive supply. As

the common-mode input voltage moves closer

n-channel input pair differential pair. The p-channel

input pair becomes inactive for the balance of the

input common mode voltage range up to the positive

supply. Because both input stages have their own

of the TS1001 is a function of the applied input

Characteristics section). Caution should be taken in

applications where the input signal amplitude is

design requires high accuracy. In these situations, it

is necessary for the input signal to avoid the

crossover point. In addition, amplifier parameters

such as PSRR and CMRR which involve the input

offset voltage will also be affected by changes in the

input common-mode voltage across the differential

pair transition region.

The second stage is a folded-cascode transistor

arrangement that converts the input stage

differential signals into a single-ended output. A

complementary drive generator supplies current to

the output transistors that swing rail to rail.

The TS1001 output stages voltage swings within

1.2mV from the rails at 0.8V supply when driving an

output load of 100kΩ - which provides the maximum

possible dynamic range at the output. This is

particularly important when operating on low supply

voltages. When driving a stiffer 10kΩ load, the

APPLICATIONS INFORMATION

Portable Gas Detection Sensor Amplifier

Gas sensors are used in many different industrial

and medical applications. Gas sensors generate a

current that is proportional to the percentage of a

particular gas concentration sensed in an air

sample. This output current flows through a load

resistor and the resultant voltage drop is amplified.

Depending on the sensed gas and sensitivity of the

sensor, the output current can be in the range of

tens of microamperes to a few milliamperes. Gas

sensor datasheets often specify a recommended

load resistor value or a range of load resistors from

which to choose.

There are two main applications for oxygen sensors

– applications which sense oxygen when it is

abundantly present (that is, in air or near an oxygen

tank) and those which detect traces of oxygen in

parts-per-million concentration. In medical

applications, oxygen sensors are used when air

quality or oxygen delivered to a patient needs to be

monitored. In fresh air, the concentration of oxygen

is 20.9% and air samples containing less than 18%

oxygen are considered dangerous. In industrial

applications, oxygen sensors are used to detect the

absence of oxygen; for example, vacuum-packaging

of food products is one example.