Re: Analog Switch question

MRW wrote:
I actually have another question regarding analog switches. I have
this image:

http://bayimg.com/OAcOnaABk

I'm trying to convert the voltage reference of a source in another
reference for the analog switch. If the source is referenced to
ground, then I would like to be able to reference it to Vcc/2 instead.

In my diagram, does it accomplish the task?

It is one general way to do it.

Also, for the capacitor values, I am assuming that I have to pick the
value based on:

- minimum frequency to pass thru the low pass filter

Yes, C1 and the parallel resistance of the two resistors connected between it and fixed voltages (assuming the analog switch sends signal to a high impedance load) have an RC time constant. At frequency 1/(2*pi*R*C) the response of this low pass filter will be 3 db down. More for lower frequencies.

- frequency relationship is also dependent on the parallel combination
of the voltage divider resistors

Yes.

- capacitor voltage rating is based on the voltage difference between
VCC/2 and reference voltage of the source

That would be the minimum. More doesn't hurt anything.

Are these assumptions correct?

Yes.

But there are other considerations.

How much supply current will these dividers consume? How regulated is that Vcc supply?

This divider scheme will add some of whatever that noise is to the incoming signals.

What is the loading effect (attenuation) of this divider load on the source impedances feeding it?

How high can these resistor values go, before leakage current through the input capacitors and the switch shift the DC operating point enough to cause some trouble? Otherwise, higher resistance has only good effects.


In many cases, it is better to use an opamp to make a low pass filtered Vcc/2 supply, and tie all the nodes that need this reference voltage to that output, with single resistors.

Also, for audio bypass capacitors, what other characteristics should I
know?

They don't catch fire? It is a fairly undemanding application. Perhaps you might define what *you* mean by the term, "audio bypass" so we are all talking about the same thing.
.

Relevant Pages

  • Re: Battery type for calibration reference
    ... My question has to do with how to provide a voltage calibration ... the best absolute voltage reference a non-technical person can buy in a ... Still, copper sulfate pentahydrate ... That's three metals ...
    (sci.electronics.basics)
  • Re: OP Frage: DC =?windows-1252?Q?Verst=E4rkung_unipolar_nah?= =?windows-1252?Q?_e_0V?=
    ... "ADC Voltage Reference: The reference voltage for the ADC indicates the conversion range for the ADC. ... selected as either AVCC, internal 2.56V reference, or external AREF pin. ...
    (de.sci.electronics)
  • Re: Marshall Mk 2 2204 Ann. Series...Blown Output fuse...Why?
    ... > B+ I assumed to be some sort of characteristic within the tubes, ... > the lines of alpha or beta when speaking about transistor based amps. ... References to B+ (DC voltage on the main amplifier circuit) and C- (negative ... aren't easily found in an on-line reference as far as I know. ...
    (alt.guitar.amps)
  • Re: RS485 is bidirectional does it mean it is fullduplex?
    ... > *) Faulty data because of different node voltage reference ... > To prevent noise over long distance cable, we can earth one side of the ... > To prevent faulty data because of different node voltage, ... > either A or B line as our common line. ...
    (comp.arch.embedded)
  • Re: Weston Cells
    ... voltage reference cells & if so, ... vintage thermocouple potentiometer & restoration depends on being able ... sneak in a few lithium cells to power the voltage reference. ...
    (sci.electronics.design)