lpf | PartQuest™ Explore

Member of the PartQuest Explore Development Team. Focused on modeling and simulation of analog, mixed-signal and multi-discipline systems covering a broad range of applications, including power electronics, controls and mechatronic systems.

Description

This Filter/Amplifier Design Example uses a single AEC-Q100 Automotive Qualified op-amp (non-inverting) for the output stage amplifier. This is combined with a single-pole RC input stage low-pass filter. As long as the op-amp has sufficient gain-bandwidth, the total in-band phase shift should be

The following calculations can be used to select the component parameter values needed to achieve the performance specifications, including the low-pass pole frequency, DC gain and the drive strength for the expected Load Resistance:

Compute Ceff = 1.0/(2*Pi*LPF-pole-frequency*10.0e3)

Choose C1 = The largest standard capacitor value that is less than Ceff

Choose C2 = A small standard capacitor value that makes C1 + C2 closest to Ceff

Compute Reff = (10**(DC Gain/20.0) – 1.0)*55.0e3

Choose R3 = closest standard resistor value to Reff

Use these rules to choose the OP-AMP part:

If Load resistance &gt; 5k Ohm and 10**(DC Gain/20.0) * LPF-pole-frequency

Choose an NCV2009 op-amp and characterize the op-amp datasheet model with GBW = 350kHz, SR_max = 0.15e6V/sec and i_shortcircuit = 8.5e-3

If Load resistance &gt; 2.0k Ohm and 10**(DC Gain/20.0) * LPF-pole-frequency

Choose an NCV2006 op-amp and characterize the op-amp datasheet model with GBW = 3.2MHz, SR_max = 1.2e6V/sec and i_shortcircuit = 19.0e-3

If Load resistance &gt; 400 Ohm and 10**(DC Gain/20.0) * LPF-pole-frequency

Choose an NCV2003 op-amp and characterize the op-amp datasheet model with GBW = 7MHz, SR_max = 8.0e6V/sec and i_shortcircuit = 96.0e-3