Hi,
Im looking for an am modulation technique using opamp. Or using fets, bjts but simple to understand and build.
Thank you!

 

Hello,

AM can not be made using an opamp.
You will need a non lineair element.

On this page from the EDUCYPEDIA you will find some links:
http://www.educypedia.be/electronics/modulation.htm

Bertus

 

I found this circuit and want to know it works or not?
OR could you give me a simple one transistor modulator without band pass filter (or coil).

 

Hello,

The circuit could work.
The fet works as a variable resistor depending on the modulation input.
The usable frequency of the carrier depends on the used opamp.

Bertus

 

Thank you!
A last question; for an 1Vpp input and 2Vpp carrier (or i can divide this if required) which values are the good for resistors?

I'dont have an oscilloscope at home and there is no possibility to try untill monday. Sorry for asking too much

 

Hello,

The Rds varies with the gate voltage.

I have taken the BF244 as example. (also attached).
The resistance changers from 100 to 300 Ohms.
If you take Rf 1K the gain will be between 10 and 3 X.
I think the carrier mus be a little lower to avoid clipping.

Bertus

 

Who banned me

I registered again to just thank you.