AW(Magnus): [sdiy] analogue phase modulation

[Magnus Danielson]

From: "JH." <jhaible at debitel.net>
Subject: Re: AW(Magnus): [sdiy] analogue phase modulation
Date: Fri, 12 Jan 2007 07:49:43 +0100
Message-ID: <001b01c73615$d98f78a0$0200a8c0 at jhsilent>

Jürgen,

> >I haven't looked in the Electronotes (at all) so I doubt it will do any 
> >good
> >to check for a similar circuit either. This one came from my imagination.
> >Just do the math and it should be obvious to you. The +/- 15V output of the
> >op-amp needs to be dampend by the 300 k resistor to match the +/- 5V signal
> >through a 49.9 k resistor.
> 
> Swapping the 300k and 50k resistors was the first thing I tried. +/-15V
> supply, too. But no rail to rail - maibe that was the problem.

It is quite obvious that it assumes +15 V and -15 V out of the op-amp. If it
doesn't you need to source a bias compensation as well reduce the output
resistor accordingly. This is an elcheapo design which may need some refinement
to be "perfect". How you tweak it is however a matter of discussion as its
main point is to convey the construction idea.

Cheers,
Magnus