Dear Forum members,

I am working as the application Engineer. I am working on modulation circuits. The circuit is built using the best CAD tools. but the output is not coming. Can any one send me the Collector modulation circuit for the AM.

I have send the circuit in the PDFrmat. Please have a look. Suggwst if any correction is required.

I want to know more about the Fooster Seelay Circuit for the FM detection.

regards
Vinay S

 

I am not familiar with "collector modulation".

Here is a link to a good article on the Foster-Seeley discriminator.

 

I am not familiar with "collector modulation".

Here is a link to a good article on the Foster-Seeley discriminator.

Vinay:

What you have in the schematic is definitely NOT collector modulation...your carrier and modulation signal are shown going to the base.

Collector modulation requires that your modulated transistor operate in Class C. If the transistor is operated in the linear mode, your two input signals will simply add...you want them to MULTIPLY.

The way do do this is to modulate the supply voltage of a Class C amplifier. There are two ways to do this....well, actually several, but two SIMPLE ways. One is with a series "pass" transistor between Vcc and the modulated transistor's collector. In this case the series transistor ("modulator") DOES need to be in class A. This method is pretty inefficient and can't give you 100% modulation. A more conventional method is to modulate the collector through a transformer...which can be driven with either a class a or class b modulator.

Eric

 

Vinay:

What you have in the schematic is definitely NOT collector modulation...your carrier and modulation signal are shown going to the base.

Collector modulation requires that your modulated transistor operate in Class C. If the transistor is operated in the linear mode, your two input signals will simply add...you want them to MULTIPLY.

The way do do this is to modulate the supply voltage of a Class C amplifier. There are two ways to do this....well, actually several, but two SIMPLE ways. One is with a series "pass" transistor between Vcc and the modulated transistor's collector. In this case the series transistor ("modulator") DOES need to be in class A. This method is pretty inefficient and can't give you 100% modulation. A more conventional method is to modulate the collector through a transformer...which can be driven with either a class a or class b modulator.

Eric

I'll send some schematics soon.

 

http://www.tpub.com/content/neets/14184/css/14184_70.htm

Here's a very conventional collector modulated stage.

eric