u/East_Friendship229

Is anybody knows the right circuit diagram for a summer op amp based am modulator using square law?? Bcuz I've made 10+ schematics in different apps like LTspice and Multisim and i still couldn't get the right Modulated output for my desired carrier and message signals. Im running out of time stressed now huhu...

Would eternally br greatful to anyone who can share their knowledge or schematics on how to make this for the following guidelines.

MODULATOR

Carrier= 20kHz

Message= 5kHz

Modulation index= 0.5-0.85

Should use Op amp based summer/buffer

Should use Diode for Non-linear switching or Square Law Modulator

Should use Op Amp like LM741 or TL081

DEMODULATOR

diode envelope detector with RC low pass filter

OUTPUT

Stable AM wave

No overmodulation/clipping

If you have any reference BOOKS you can recommend will help alot in computing for values or Schematic diagrams WILL GREATLY APPRECIATE IT! THANKYOU!!!

So I'm trying to make an AM MODULATOR with the following guidelines:

Modulating Signal: 5 kHz Sine Wave.

• Carrier Signal: 20 kHz Sine Wave.

• Circuit Architecture:

o Modulator: Op-amp based summer/buffer followed by a non-linear switching or square-law diode modulator.

o Demodulator: Diode envelope detector with an RC low-pass filter.

• Output Requirement: A stable AM wave with a modulation index between 0.5 and 0.85 without significant overmodulation or

clipping.

II. Project Guidelines

Phase I: Design & Simulation

• Calculate the required components for the modulator circuit.

• Calculate the required components for the RC filter in the envelope detector. Ensure the time constant satisfies the condition to

avoid excessive ripple and clipping.

• Use software (e.g., LTspice, Multisim, Proteus) to verify that your 5 kHz signal is successfully modulated and recovered after

demodulation.

Phase II: Hardware Construction

• Construct the circuit on a PCB.

• Use standard op-amps (e.g., TL081 or LM741).

Phase III: Testing & Documentation

• Capture oscilloscope screenshots of:

The Modulating and Carrier signals.
The resulting AM Wave (Time Domain).
The Demodulated Output vs. the Original Message.

The problem is even though I've calculated the right bandpass filter values i still couldn't get the right output. If anything can share their knowledge it would be greatly appreciated huhu!

Im trying to make a Summer/Buffer Am modulator using Square Law

Is anybody know how to fix this schematic for Summer and Square law AM MODULATOR