TS1002/TS1004

TS1002/4 Rev. 1.0

Page 7

PIN FUNCTIONS

Pin

Label

Function

TS1002

MSOP

TS1004

TSSOP

1, 7

1, 7, 8, 14

OUT

Amplifier Outputs: A, B – TS1002; A, B, C, D – TS1004

4

7

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, 5

3, 5, 10, 12

+IN

Amplifier Non-inverting Inputs: A, B – TS1002; A, B, C, D – TS1004

2, 6

2, 6, 9, 13

-IN

Amplifier Inverting Inputs: A, B – TS1002; A, B, C, D – TS1004

8

14

Positive Supply Connection. Connect a 0.1µF bypass capacitor from

this pin to analog GND.

THEORY OF OPERATION

The TS1002 and the TS1004 are fully functional for

consist of two 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

negative supply to approximately 0.4V below the

positive supply. As the common-mode input voltage

activates the 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

offset voltage of these amplifiers is a function of the

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 amplifiers’ 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 amplifiers’ output stage voltage swings within

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

output load of 100k

Ω - which provides the maximum

possible dynamic range at the output. This is

particularly important when operating on low supply

voltages. When driving a stiffer 10k

Ω 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