Re: AM Modulation

On Mon, 20 Mar 2006 08:06:47 -0800, Don Bowey wrote:

On 3/19/06 5:48 PM, in article ORnTf.131$rg7.49@xxxxxxxx, "Tim Williams"
<tmoranwms@xxxxxxxxxxx> wrote:

"Tim Williams" <tmoranwms@xxxxxxxxxxx> wrote in message
news:jPnTf.130$rg7.93@xxxxxxxxxxx
Outside of saturation, constant
current devices such as pentodes and transistors will tend to have less
modulation (higher PSRR) than triodes or transistors wired for a resistive
characteristic.

In fact the perfect example is the quintessential analog voltage multiplier
circuit, a FET in the "linear" range (typically fractional volts Vdss). Id
is jointly proportional to Vds and Vg, not counting nonlinearities, which
can be smoothed out with a little help.

That's an example of a class A device (current always flowing), high-level
modulated (by varying Vds) and multiplies two signals, hence capable of
producing AM. Viola ;-)

By magic? Explain how a linear device operating linearly, will generate sum
and difference frequencies.


(a + jb) * (c + jd) = ac - bd + jbc + jad

Cheers!
Rich
--
Elect Me President in 2008! I will:
A. Fire the IRS, and abolish the income tax
B. Legalize drugs
C. Stand down all military actions by the US that don't involve actual
military aggression against US territory
D. Declare World Peace I.


.

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