To change the frequency in a circuit using a MOSFET, it is essential to specify the application and desired frequency range. The discussion emphasizes the importance of understanding the power levels involved and the specific circuit configuration. Participants inquire about the context of the frequency change, suggesting that clarity on the application is crucial for providing accurate guidance. The conversation highlights the need for detailed information to offer effective solutions. Ultimately, the effectiveness of using a MOSFET for frequency modulation depends on the specific requirements of the circuit.