RC4558: Questions about the common mode input voltage range of operational amplifiers

SHENG YANG

Part Number: RC4558
Other Parts Discussed in Thread: LM358LV, LM321LV, LM321

HI.Team.

I am currently building a differential amplification circuit using an RC4558 with a 5V supply and sampling current values. Please let me know if the circuit is working properly. Can the common mode voltage input range meet the requirements? Thank you.

6 months ago

0 Ron Michallick 6 months ago

TI__Guru*** 145766 points

Hello Sheng Yang,

In addition to VCM concern, the power supply is too low. The recommended minimum is 10V

If accuracy is not critical, then LM321LV or LM358LV could be used.

0 SHENG YANG 6 months ago in reply to Ron Michallick

Expert 1190 points

HI.Ron

Thank you for your reply.The current accuracy requirement is not too high, if I use LM321, according to the parameters in the figure below, can it meet my circuit needs? The circuit is a 5V single power supply with high side current sampling.Or if there is a suitable op-amp model to recommend.

+1 Ron Michallick 6 months ago in reply to SHENG YANG

TI__Guru*** 145766 points

Sheng,

VCM is 5V * 100k/ (33k + 100k) = 3.76V

LM321LV Max VCM is 5V - 1V = 4V ; this is not a hard limit , the op amp still works if VCM is a little higher.

3.76V < max of 4V

If you want a little more VCM margin, bump up R1, R2 a little

0 SHENG YANG 6 months ago in reply to Ron Michallick

Expert 1190 points

Thank you for your reply.

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RC4558: Questions about the common mode input voltage range of operational amplifiers