[sdiy] Op-amps CA3140 v. TL074

[Ian Fritz]

At 01:58 PM 7/29/2010, Tim Daugard wrote:
>Has any one used the CA3140 or more, compared it to the TL074? The data 
>sheet says the CA3140 has a MOSFET input. Is that input anything special?

Yes it is. A MOSFET input is over 10^14 Ohms. You cannot come close to this 
input performance in any other opamp without paying a huge price.  The 
CA3140 is still in production and currently available for ~ $2. I use it 
for my TGTSH module and it easily outperforms high-performance JFET opamps 
such as the OPA602, which costs over $9.

Replace it with a TL074 ?!?!?!  No way.

Ian