OPA333

3V

NTC

Thermistor

1 M

Ω

60 k

Ω

100 k

Ω

1 M

Ω

V

1

−In

V

2

+In

R

1

R

2

2

3

5

6

1

R

2

OPA333

OPA333

INA152

V

O

V

O = (1 + 2R2/R1) (V2 − V1)

R

1

100k

Ω

1/2

OPA2333

RA

Inverted

V

CM

+V

S

INA321(1)

+V

S

V

OUT

+V

S

+V

S

+V

S

OPA333

+V

S

1/2 V

S

dc

3

2

1

4

5

6

G

TOT = 1kV/V

G

INA = 5

G

OPA = 200

f

LPF = 150Hz

f

HPF = 0.5Hz

(provides ac signal coupling)

V

S = +2.7V to +5.5V

BW = 0.5Hz to 150Hz

f

O = 0.5Hz

Wilson

V

CENTRAL

(RA + LA + LL)/3

7

ac

1/2 V

S

R

2

100k

Ω

1/2

OPA2333

LL

+V

S

R

3

100k

Ω

1/2

OPA2333

LA

R

4

100k

Ω

R

9

20k

Ω

R

6

100k

Ω

RL

+V

S

+V

S

1/2

OPA2333

1/2

OPA2333

1/2

OPA2333

C

4

1.06nF

C

3

1

µF

R

14

1M

Ω

R

12

5k

Ω

R

13

318k

Ω

R

7

100k

Ω

R

8

100k

Ω

R

10

1M

Ω

C

2

0.64

µF

R

11

1M

Ω

C

1

47pF

R

5

390k

Ω

NOTE: (1) Other instrumentation amplifiers can be used,

such as the INA326, which has lower noise,

but higher quiescent current.

OPA333A-EP

,, OPA2333A-EP

SGLS383B – APRIL 2007 – REVISED JUNE 2008 ............................................................................................................................................................ www.ti.com

Figure 7. Thermistor Measurement

Figure 8. Precision Instrumentation Amplifier

Figure 9. Single-Supply, Very-Low-Power ECG Circuit

12

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