There could be several reasons why your non-inverting amplifier is not working as expected when the input voltage is a sine wave with an amplitude over 400mV and a frequency of 41.3kHz. Here are a few possible causes:
Saturation: The amplifier might be saturating due to the high input voltage. If the input voltage exceeds the maximum output voltage range of the amplifier, the output will be clipped, resulting in distortion. Check the datasheet of your amplifier to ensure that it can handle the desired input voltage range.
Bandwidth Limitations: Non-ideal amplifiers have a limited bandwidth, meaning they are not able to amplify signals accurately above a certain frequency. If the frequency of your input signal (41.3kHz) is beyond the bandwidth of the amplifier, it may introduce distortion or attenuation. Verify the bandwidth specifications of your amplifier to ensure it can handle the desired frequency range.
Gain Bandwidth Product: Amplifiers have a parameter called the gain-bandwidth product (GBP), which determines the maximum gain that can be achieved at a given frequency. The gain of the amplifier decreases as the frequency increases. If the GBP of your amplifier is not sufficient to maintain the desired gain at 41.3kHz, the output may not accurately represent the input. Check the GBP specification of your amplifier and calculate the expected gain at the desired frequency.
Input Impedance Mismatch: The non-inverting amplifier requires a high input impedance to prevent loading effects on the input signal. If the input impedance of your amplifier is not high enough, it can affect the performance of the amplifier, especially at higher frequencies. Ensure that the input impedance of your amplifier is suitable for the source impedance of the input signal.
Noise and Interference: High-frequency signals are more susceptible to noise and interference. If there is significant noise or interference present in your circuit or in the environment, it can affect the performance of the amplifier and result in distorted output.
It's important to thoroughly review your circuit design, amplifier specifications, and signal characteristics to identify the specific issue causing the non-inverting amplifier to malfunction.