This is a simple Binary Pulse Amplitude Modulator. The digital input is connected to the Gate of the Nmos transistor while the Carrier wave is applied on the Drain. When the input is 1 , the transistor becomes active and the carrier wave propagates to the output, while when the input becomes 0 ,the transistor shuts off and the output becomes 0 .Using this technique we can produce the two PAM symbols required for transmition
