Op Amp Responses

Feb 08, 2013

The graph below shows typical relative frequency responses for a variety of popular op amps covering a wide range of GBW (from 5 MHz to 1.5GHz) in a standard 40dB non-inverting amplifier configuration. Supply voltages were either +/- 9V or +/- 5V depending on the device capability. The output voltage level for the tests was 0.4Vpeak so that responses at least up to the -3db point were not limited by slew-rates. A Digilent Analog Discovery scope (10 MHz BW) with the Bode plotting function of the Waveforms software was used to obtain the frequency response. The Analog Discovery function generator level was passed through a -40dB resistive attenuator which helps to isolate the function generator from the amplifier input providing good input noise characteristics. Since the Bode plot represents the response relative to the attenuator input, the low frequency DC gain ideally would be 0 dB. Due to the attenuator network and input circuit of the op-amp, the plots show a ~ -0.6 dB relative level at low frequency. Therefore the f3db line is shown as -3.6dB. The testing configuration is shown below the graph: