Question

Please Explain this amplitude modulator we built on multisim and how it operates. Be as detailed as possible

.... 3Vpk..... 2000kHz 111 . ZAPHOTO_DIODE_RATED XSC1 VCC R5 100k 01. P000 - 3491 3680K R6+| 11:34700T220pF 20KHZ. PHOTO TRANSISTOR RATED R10 100KO 100k On 100KO - TOV. ..Vcc

Answer 1

In the Question it has been asked to Explain the Arablitede Madelator circaciebag that ulas built on Multisim and to descricke its operation. 1. The circuit given here allowes the transmission of audio signals to AM radio signal. It consists of an RF Oscillatar operating in the AM broadcast band and it ako has the modulator stage that mixes the incoming audio signal with the Radio Frequency signals. The signal on the output has an AM. Component which is ficked up by the AM Hadio receivere.

The transmitter in the circuit consists of on Oscillative I stage as with 2N3904 transistor and Modulator on Buffer stage with the Op-amp connected to Vcc and Voo. The can see that the transistor 2N3.904 is kiased with the Resistor R5 (look ) and Ru (680kb). L, Cg and C3 forms the tank circuit with the feedback network. RF voltage at the junction of C₃ (.2.20F) and La (2.7mh) drives the kuffer ou modelator stage. C6 (47p F) is an Audio and Radio Frequency bypass Capacitor. Lag Cy and CG forms the took circuit fore beffer stage RF is. then taken from the output stage of of-omf and fed to - Xsci to sense the output eignal. This signal is fed back to the Emitter junction of Transistor Qf which sendes the signal. If the signal generated is greater then 100 then it is modulated, otherwise the photo diode u turn on . and the signed is fel- back again to the reference input.

Audio is now fed from modulatore to via output of U₂ and isolation resistor R7 (sokab). An AM signal now appears at the collector ciruit of Qg with on RMS - Voltage equal to about 0.7 times of the collector voltage seen at the transistor Q1 . . As the modulation obtained from the circuit is Eneasily limited as conventional audio sowies. The ces cuit here demonstrates the principle of an AM tronsmitter with a suitable audio drive level which produces a well modulated AM signal. 2 . La and La resonates well with the capacitors and it obtains the desired level of output frequently