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LMH6642: Supply of strain gauge full bridges

Jan Bock
Intellectual 2830 points
Part Number: LMH6642
Other Parts Discussed in Thread: INA317, INA188, INA333, PGA281, PGA280, PGA204

Hi, 

My customer tries to improve his design of an amplifier card. His main interest is to improve the supply of strain gauge full bridges:

The current system looks like follows: 

  • Strain gauge impedance = 350 Ω 
  • 5V Sensor bridge supply
  • 12 LMH6642 (SOT-23) + voltage ref from a microcontroller (likely with an internal DAC ) = means he can supply 4 bridges with one LMH (4*350 Ω / 5 V = 57 mA)

I already talked with an other FAE about this and we gathered the following points for improvement:

  • lower amount of OP if a OPAMP is used that can drive more current
  • The bandwidth of the LMH6642 is from our view not needed
  • The customer also want to reduce the size so do we have a OPAMP can driving higher currents
  • The supply must be bipolar 
  • low 1/F noise is needed
  • low current and voltage noise is needed

So do we have some advise for the customer to improve his application. Which device would fit best for the application. 

Thanks for looking into this 

Jan