4066 Bilateral Switch questions

[Pete]

Hi group,

I am a genuine newbie to electronics trying to understand the operation of
an 4066 IC bilateral switch. It has 4 switches, only two of which I need to
use. For each switch, there is three connections - ctrl, I/O and O/I. Here's
my questions:

1. what do these connections actually mean?
2. why do you need 3 connections to make a switch - I though 2 was
sufficient?
3. the first switch also has two other connectors labelled vDD and vSS -
what do these mean?

This is all gobbledegook to me so all assistance is greatly appreciated.

 

[John Popelish]

Hi group,

I am a genuine newbie to electronics trying to understand the operation of
an 4066 IC bilateral switch. It has 4 switches, only two of which I need to
use. For each switch, there is three connections - ctrl, I/O and O/I. Here's
my questions:

1. what do these connections actually mean?

Ctrl is the control line that turns each switch on or off. If the
control line has the same voltage as the Vss pin, the switch is off.
If it has the same voltage as the Vdd pin (ordinarily 3 to 18 volts
more positive than Vss) the switch is on.

I/O and O/I mean that either of these can be signal in and either can
be signal out. The voltage on both should be anywhere between Vss and
Vdd at all times.

2. why do you need 3 connections to make a switch - I though 2 was
sufficient?
3. the first switch also has two other connectors labelled vDD and vSS -
what do these mean?

Those are the power pins for the inverter logic inside the chip. When
you take a ctrl pin high, the inverse (low) is also needed,
internally, and vice versa. These switches are made up of N and P
channel mosfets, and it takes a positive voltage to turn an N channel
mosfet on, and a negative voltage to turn a P channel mosfet on.
Since these switches are made to conduct in either direction, they are
made up of a P channel and an N channel mosfet connected in inverse
parallel. The data sheet covers this pretty well.

http://www.fairchildsemi.com/ds/CD/CD4066BC.pdf

 

[John Popelish]

Hi group,

I am a genuine newbie to electronics trying to understand the operation of
an 4066 IC bilateral switch. It has 4 switches, only two of which I need to
use.

(snip)

Be sure to tie the unused ctrl lines to either Vss or Vdd, to keep
them from floating around and causing high current consumption by the
internal inverters.

 

[Kevin Aylward]

Hi group,

I am a genuine newbie to electronics trying to understand the
operation of an 4066 IC bilateral switch. It has 4 switches, only two
of which I need to use. For each switch, there is three connections -
ctrl, I/O and O/I. Here's my questions:

1. what do these connections actually mean?

A switch path has two terminals, any one of which can be either an input
or output, hence I/O, O/I

2. why do you need 3 connections to make a switch - I though 2 was
sufficient?

How do you propose to turn the switch on and off without a voltage
control input?

3. the first switch also has two other connectors labelled vDD and
vSS - what do these mean?

VDD - most positive supply voltage
VSS - most negitive supply voltage


Kevin Aylward
[email protected]
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
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