What is the purpose of a buffer in a transmitter?

A buffer in a transmitter serves primarily to isolate the oscillator from the power amplifier. This isolation is crucial because it allows the oscillator to operate without being influenced by the loading effects of the power amplifier. When the power amplifier is connected directly to the oscillator, variations in load could cause instability in the frequency or amplitude of the oscillator signal, leading to poor performance. By utilizing a buffer, the impedance between these two components is matched, ensuring that each can perform its function optimally and without interference from the other. This separation enhances the overall efficiency of the transmitter and helps maintain consistent signal quality, which is vital for effective communication.