AM Modulator

This circuit uses two signal generators to simulate an Amplitude Modulated RF carrier wave. The output can be used to simulate the response of LC and tank circuits. Two signal generators are used in this circuit, one representing a high frequency (200kHz) RF carrier, VG2, the other signal generator is used to inject a 1KHz audio signal. The two si

gnals are mixed and amplified by the transistor and an amplitude modulated signal appears at the collector of the BC548. The DC component is removed by C2 and R3 and the RF output now appears across the load resistor R3. Waveforms below are produced using Tina. To produce an output in Spice Opus start the program and load the new vmod. cir The modulated signal appears across R3 which is now node 3 and earth. After loading the circuit the command "listing" will display the netlist. The command "run" will then simulate the circuit, "display" will print a list of all variables in the circuit. The command plot v(3) will display the AM wave between node 3 and 0 i. e. the load resistor R3. Note to speed up simulation, the RF carrier has been limited to 200KHz only, and the output waveform just shows two complete cycles of the audio wave, i. e. 2ms as the modulating frequency is 1k. There will be some spice tutorials shortly on my pages.

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