The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: Winfield Hill
Subject: Re: circuit wanted-SQUARE PULSE GENERATOR
Date: 26 Nov 2002 13:48:05 -0800
Organization: Rowland Institute
References: <1038144646.265208@athprx02> <email@example.com> <firstname.lastname@example.org> <email@example.com>
X-Newsreader: Direct Read News 4.11
>Jim Thompson wrote...
>> I've been using the 1X/2X approach for at least 35 years in on-chip
>> VCM's (voltage-contolled multivibrators).
>> Here's a question for all you lurkers:
>> Delay in the comparators (in a 555 or otherwise) affect the linearity
>> of the control curve, particularly at high frequencies (I've built
>> these at frequencies as high as 50MHz).
>> Can anyone here mathematically describe the effect as a function of
>> delay and operating frequency? And then offer a solution? I can.
> Well let's see, there's a delay in the integrator dV/dt output
> (if one is implemented as an opamp integrator) and there's a
> delay in the comparator and current-switching circuitry, let's
> call all these delays td. If I is the charge/discharge current
> and V is the low-frequency charging-voltage excursion, then we
> get f = I / 2C V (1 + 2td f), which equivalent to the comparator
> threshold voltage growing by the fraction 2td/T where T = 1/f is
> the output period. So it would seem a correction that slightly
> reduces the threshold voltage as a function of I would do the job.
Ah, a resistor in series with the capacitor! Does the same job as
lowering the threshold voltage as a function of current, nice!!!
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup