products selection of OP amp

Hi Mark,

Have you taken a look at our parametric search table tool? http://www.ti.com/amplifier-circuit/op-amps/precision/products.html

Try that link, you can compare many precision amplifier specs including package and price!

Hi Mark,

Absolute value circuits become less ideal as the input frequency is increased. That is because the gain of the op amp falls off with increased frequency, limited slew rate and capacitances in the circuit affect the levels of precision that can be achieved. The results obtained may be very good at 50 Hz, or even a few kilohertz, but by time the frequency is 20 kHz higher distortion can result. The level of performance varies with the absolute value circuit topology and some are better than others.

My recommendation for best 20 kHz performance with a moderate bandwidth op amp such as the OPA1678 is to use the Figure 1 circuit shown in the SBOA068 TI Applications Bulletin. The OPA1678 is a low cost, high performance op amp that should work well in the Figure 1 circuit. I do not obtain as good of simulation results at 20 kHz with the circuit you show, which is the Figure 5 circuit in the bulletin. 

Here is a screenshot of the TINA simulation results for the Figure 1 circuit using the OPA1678 dual op amp.

Here's my TINA-TI simulation circuit file:

OPA1678_ABS_sboa068_Fig1.TSC

Regards, Thomas

Precision Amplifiers Applications Engineering