cd4066 output current?

[crosslakeguy]

Having a rough time decoding the data sheet......the only reference I can see is in ua........ then when I convert that to ma the number is so low that it looks like it should burst into flames just being in the same room as electricity.... I was going to use it to make a high or low output driver, thinking a "switch" would have some ability t drive current. was first going to use a unl2003 but realized I would only have a negative output, my logic is positive...... I think there is a pos output version but could not find one. thinking the best of both worlds would use a cd4066, not looking so good though..... first used a cd4050 thinking a buffer/driver should have some capability of driving, but yet again the answer was no. so in addition to the original question about the current of the cd4066, Is there a decent IC capable of driving more than 10ma? preferably cmos logic........ didn't realize I would need to build a power station to drive a simple opto-isolator with positive logic

 

[Nigel Goodwin]

A CMOS switch is for switching signals, not for supplying current.

You need to be far more detailed about exactly what you're trying to do, with a diagram if possible.

 

[crosslakeguy]

I purchased a motor driver board which has optical isolators, to my understanding, they draw around 30ma similar to an led..... my logic is positive and would like to output a positive signal that can drive 30ma or more. the other motor drivers I have are "logic"level inputs..... so no problem.... this board isn't "logic" level...... thought the cd4066 bilateral "switch"
is capable of driving current, but cannot see in the data sheet any data on current

And It doesn't need to be cmos I guess

 

[Nigel Goodwin]

Why not simply use the ULN2003 you mentioned earlier, and connect the +ve side of the opto-isolator to your positive supply?.

 

[crutschow]

A simple solution would be to use a small NPN transistor (such as a 2N2222) as a emitter follower buffer but that reduces the output voltage by about 0.7V. If that's a problem then you could use an NPN driving a PNP.

What is the exact input voltage and current requirement for the motor driver board?

 

[crosslakeguy]

I could use a unl2003 for a "fix" for this board, however my other controlers require positive logic signal. was simply looking for a single chip driver that can drive around 30ma +5v from positive logic. maybe I need to look in my books for an amplifier ic.... my board has 6 channels. didn't want a bunch of resistors and transistors just to drive stinking optos.

 

[Nigel Goodwin]

I could use a unl2003 for a "fix" for this board, however my other controlers require positive logic signal. was simply looking for a single chip driver that can drive around 30ma +5v from positive logic. maybe I need to look in my books for an amplifier ic.... my board has 6 channels. didn't want a bunch of resistors and transistors just to drive stinking optos.

Wouldn't it be easier to modify the boards so the opto's aren't grounded?, which seems pretty pointless for an opto anyway.

As crutschow mentioned, a simple NPN emitter follower would do, the 0.7V lost wouldn't matter for an opto - does your board have limiting resistors on, or do you need to add those as well?.

 

[crutschow]

Perhaps something like this line driver would work.

 

[Nigel Goodwin]

Perhaps something like this line driver would work.

Or use a PIC with a few lines of code

But, as usual, the thread is rather vague - we've no idea what his source is?, perhaps that can already provide enough current? (you probably don't need 30mA).

 

[crosslakeguy]

the source is a cd4050 which is driven by a cd4043 @5v . the item driven is a "cheap" Chinese stepper motor driver. the cd 4050 cannot drive the opto-isolators. the $150 gecko drive Im sure would work fine...... but the fact is however it is made, it needs more current. . and yes Nigel, a PIC could replace the board I have made.....but where is the fun in that.........

and just like behind every little problem, with a larger problem built in.......
If that cheap Chinese board wants more power, that's what it is going to get MORE POWER.....
every electronic component has condensed smoke manufactured into them, you need to be carefull not to let it out.....

I think crutschow may be on to something with the tri-state driver.....need to look into it ..

still have not had any one say how much current a cd4066 can drive

 

[audioguru]

The datasheet for a CD4066 says that its maximum input into one switch is 10mA and it has spec's for its on-resistance vs supply voltage.
You can connect its switches in parallel for up to 40mA input.

 

[shortbus=]

Or use a DG202 or DG201. They are capable of 30mA, if I remember right.

 

[Mike odom]

A simple solution would be to use a small NPN transistor (such as a 2N2222) as a emitter follower buffer but that reduces the output voltage by about 0.7V. If that's a problem then you could use an NPN driving a PNP.

What is the exact input voltage and current requirement for the motor driver board?

wouldn't the PNP also drop .7v from it's emitter to collector?

 

[Mike odom]

If the optos need 30mA, does this mean that they have a limiting resistor on the board? If not, the voltage doesn't matter but you have to limit the current with a series resistor.

 

[audioguru]

wouldn't the PNP also drop .7v from it's emitter to collector?

An NPN emitter-follower has its collector at the positive supply, the base is the input and the emitter is the output which is 0.7V less than the base voltage.
A PNP emitter-follower has its collector at ground, the base is the input and the emitter is the output which is 0.7V more than the base voltage.
When both emitter-followers are used then the base-emitter voltages cancel and the output voltage is almost the same as the input voltage.

 

[Mike odom]

AG, I'm not following how you would hook them up? NPN driving the PNP?
In a pre-biased audio circuit, sure. But as a source voltage for optos?
Can you 'splain further?

 

[Mike odom]

ok, had momentary brain fart... was thinking the pnp base resistor in series between two transistors.

Like this (R3 is opto current limit resistor):

 

[crosslakeguy]

Perhaps something like this line driver would work.

One of the most important lessons I learned today is that it seems low level logic is capable of driving more current, the IC you listed, which is the same as an 74act244. octal driver. I am going to swap out the cd4050 for a cd4049, and drive low, which more than quadrulples the power. The driver listed above is one of the few that has equal high and low level current output. the dg202 is also a good choice as a replacement for a cd4066.. several people have suggested connecting outputs in parallel, but no-one has suggested piggy-backing IC's. other than the obvious reason of being able to drive 2 chips........

 

[rc3po]

ok, had momentary brain fart... was thinking the pnp base resistor in series between two transistors.

Like this (R3 is opto current limit resistor):

Aren't the transistors in the wrong places? Doesn't the Vb of the PNP have to be at least .7v less than the emitter?

 

[Nigel Goodwin]

still have not had any one say how much current a cd4066 can drive

That's because a CD4066 would be the entirely wrong type of device to use, and no one conversant with electronics would even consider it

Case in point, the original David Tait design PIC programmer (the 'father' of PIC programmers), which was pretty soon redesigned correctly by others (David was a programmer, not an electronics designer).