Help Verify this Simulation

[kunene]

Hi guys, Im trying to simulate the circuit from this link:**broken link removed**

But the problem is I really don't get the same waveforms as the shown in the link, the output signal at the negative portion, does not reach -4.5 volts(as desired), and also the zero portion(when the pulse is at zero) is not entirely zero, some portions are negative.

what is it that I should change to get the same waveforms as in the link above?

The attached files might be of help to get what I have done so far.

 

[ericgibbs]

hi k
For a negative half cycle of the 40Khz sine, you must have a -Vee to the 4066, look as this image and asc file

EDIT:
Or offset the sine wave by +2.25V and reduce the sine wave Vpk to 2.25V. OK.?

 

[kunene]

hi k
For a negative half cycle of the 40Khz sine, you must have a -Vee to the 4066, look as this image and asc file

EDIT:
Or offset the sine wave by +2.25V and reduce the sine wave Vpk to 2.25V. OK.?

Hi Eric

First let me say thanks for helping. But in this case, from ur asc file, the output is not switched, it just follows the input, which is not what is required.
What I want is the output signal to be zero during the marked region from the attached file in Vd signal. Meaning to say, when Vd is zero, Voutput should also be zero.

 

[ericgibbs]

hi,
Will look closer, I'll be back...

EDIT:
You need to load the OUTPUT to 0V with say a 10K resistor, else the OUTPUT is 'floating'.

OK.?

 

[kunene]

The sine wave in this case is the signal that I want to switch on and off, and the amplitude will be around 4.5V. So if I needed to reduce the voltage of the sine wave, I think I would require extra circuitry, wouldnt I?

 

[ericgibbs]

The sine wave in this case is the signal that I want to switch on and off, and the amplitude will be around 4.5V. So if I needed to reduce the voltage of the sine wave, I think I would require extra circuitry, wouldnt I?

If you are limited to say +5V enable signals.
I will post an image

EDIT:
this shows a simple resistive divider,, 9VppK in 4.5Vppk out.
If you post your circuit I could make some suggestions.

 

[kunene]

I mean the sine wave is the one that I want to see in the output, but depending on width of the pulse (in this case, the vd pulse), it will be same as sine wave when the pulse is at its high, and be zero when the pulse is zero.

Alright.....

 

[kunene]

I just spotted something that I missed, in the link that I provided it comes: "Two switches inside the quad analog switch CD 4016 are used in the circuit. When the enable input of one gate is at high, then the input will appear at the output."

And I only used one switch, but I included another switch in the attached asc file. you can see that the graph changes a bit, but still not perfect. the output goes to -0.7v where it was supposed to be zero, does that -0.7v have anything to do with the components used? and still the negative portion does not reach -4.5v.

 

[kunene]

If you are limited to say +5V enable signals.
I will post an image

EDIT:
this shows a simple resistive divider,, 9VppK in 4.5Vppk out.
If you post your circuit I could make some suggestions.

ohh, I did not see your "EDIT" before I posted the above post, this looks good, It might work. let me just try to simulate in this end.

 

[ericgibbs]

hi,
As I said your sine wave input is swinging from +4.5V thru 0V then down to -4.5V, you cannot control the negative half cycle with the 4066 with only a +5V supply, you need to connect the 4066 0V pin to a -5V supply for it to work.

Also two 4066's are not required.

Do you follow OK.?

EDIT:
To offset the negative half cycle and use only a +5V supply to the 4066 , you could use this circuit.

You must also ensure that the full swing of the sine wave voltage does not exceed the +5V, so add a resistive divider at the input of the 4066.

 

[kunene]

yes I follow, now im modifying the circuit. will give you feedback in a while.

 

[kunene]

We definitely put this problem to bed. thanks Eric, you nailed it, as always. thanks a lot.