--- In LTspice@..., John Woodgate <jmw@...> wrote:
In message
<CALBs-TjHj0Lx41mORJzKDHfd+kPbe+U=GYY+WhLO1MsP+7LKGw@...>,
dated Mon, 15 Apr 2013, Andy <Andrew.Ingraham@...> writes:
That's an interesting hypothesis, but I think it's not true. I think
that varying R2 (while a DC signal is placed at the input to the
op-amp) is very different than simply applying a varying signal to the
amp's input. I suspect that if you try it (with .TRAN analysis) you
would see different results.
Doesn't varying R2 just vary the gain by which the DC input voltage is
multiplied to produce the output? So if R2 varies sinusoidally at
frequency f, the output will be a sine wave at frequency f.
Vout = Vin*R2/R1
If R2 = R*sin(2*pi*f*t), Vout = (Vin/R1)*R*sin(2*pi*f*t)
--
John,
This is true only at low frequcncies, and that's the reason the OP wants to know the effect as a function of frequency. Obviously, he needs to do this in the time domain for each frequency of interest. This type of problem has been discussed in this group relative to switch mode power supplies. In effect, time domain methods are used to get a pseudo frequency domain response.
Rick
