[FAQ] Precision amplifiers for lab and field instrumentation

Other Parts Discussed in Thread: OPA2206, THP210, OPA2182, OPA2387, OPA197, OPA391, INA821, INA826, LPV821, OPA369

PRAMPS in lab and field instrumentation

Analytical lab equipment can be used for early detection of diseases and drug development in life sciences. Apparatuses for mass spectrometry, spectroscopy and chromatography require a high level of accuracy. Precision amplifiers are a critical part of the design for signal conditioning and analog signal processing.

Field instrumentation equipment includes a broad range of measurements including liquid analysis, pressure, and temperature monitoring. Portable field instruments such as data loggers and process control require low power and low noise to maximize efficiency without degrading the accuracy of the measurement.

 

Figure1. Typical block diagram for signal conditioning block with high accuracy   

 

 

In figure 1 the OPA2206 provides the protection (up to 40V) which may be needed against voltages that are much higher than the operating range of 36V. The OPA2206 has super beta input transistors which reduce the input bias current substantially compared to other bipolar devices. As a result of its super beta inputs, the OPA2206 has a high input impedance and a very low current noise which make it versatile for various analog signal processing including buffering high voltage signals.

In the next stage, the THP210 is used as a differential amplifier to drive a high-resolution ADC. The very low noise floor and the differential output increase noise immunity which minimizes the impact on the ADC and helps maintain the overall system ENOB to adequate levels. In addition to the THP210 as a differential driver, the OPA2182 is used as a reference buffer. The zero-drift op amp provides a very low offset drift of 12nV/C and allows the system designer to avoid complex calibration schemes. The zero-drift topology virtually eliminates the 1/f component thereby increasing the accuracy of the overall system.

 

 

Table 1. Recommended precision op amps for lab instrumentation

 

Specifications

OPA2387

OPA197

THP210

OPA391

System benefit

Super precision

Mux friendly

Ultra-low noise

Micro power zero drift

Supply Range (V)

1.7 to 5.5

4.5 to 36

3 to 36

1.7 to 5.5

GBW (typ, MHz)

5.7

10

9.2

1

Input Offset (max, µV)

15

100

40

45

Input Offset Drift (typ, µV/°C)

0.003

0.5

0.1

1

Noise @ 1kHz (typ, nV/rtHz)

8.5

5.5

3.7

60

Iq per Channel (max, mA)

0.57

1

0.95

0.024

Output Current (typ, mA)

55

60

31

60

 

 

Table 2. Recommended precision instrumentation amplifiers for lab and field instrumentation

 

 

Specifications

INA821

INA826

System benefit

High input Z, High CMRR

Low power high CMRR

Supply Range (V)

4.5 to 36

4.5 to 36

GBW (typ, MHz)

5

1

Input Offset (max, µV)

35

150

Input Offset Drift (typ, µV/°C)

0.4

2

Gain drift (ppm / °C)

5

1

Noise @ 1kHz (typ, nV/rtHz)

7

18

Iq per Channel (max, µA)

650

200

For portable field instrumentation equipment, precision low power op amps help improve the system efficiency while maintaining signal integrity. 

Table 3. Recommended very low power precision op amps

Specifications

LPV821

OPA369

System benefit

Very low drift, nano power

Zero cross over very low power

Supply Range (V)

1.7 to 3.6

1.8 to 5

GBW (typ, kHz)

8

12

Input Offset (max, µV)

10

0.75

Input Offset Drift (typ, µV/°C)

0.02

0.4

Noise @ 1kHz (typ, nV/rtHz)

215

290

Iq per Channel (max, µA)

0.650

0.8