I am creating a differential amplifier that deals with inputs ranging from 0-50mV. I have been using an LM324N, but when I get to <100mV, the noise interferes too much (I have decoupling caps and have terminated the unused opamps). I need a high precision opamp that can deal with <100mV, but have not dealt with them before. Is OPA277P an acceptable opamp that will fit my spec? I am providing +-15V to +-Vcc.

 

The OPA277 is a good opamp for precision work. The Linear Technology, Inc. LT1793 is good, too, especially if you are dealing with very high source impedances and need extremely low input bias current. The LT1128, on the other hand, is excellent when working with low-impedance input sources and has extremely low input voltage noise.

 

http://www.linear.com/products/low_noise_amplifiers

 

NE5532?

 

For your LM324 circuit, are you using the 2-opamp or 3-opamp implementation?

The 5532 is an old and dear friend, but it isn't the best choice for DC precision. This is where Analog Devices and Burr-Brown (now TI) shine. Relatively new kid Linear Tech also is strong in this area. Not a big Maxim fan.

Also, consider an integrated instrumentation amplifier. A bit more money, but you get precision-matched, laser-trimmed, temperature-tracking resistors built-in.

ak

 

I have a lot of new OPA627BM, each tested to have offset of approximately around +100 uV. If you are interested, let me know and I'll send them to you.