AD633 as amplitude modulator - not working

[Peet1]

Hi,

Please can someone help on what has got to be a simple oversight by me.

I am using the AD633 in spice as an amplitude modulator, but it's just giving me a rubbish output. Output is a few mV when the input is a few V, and it is not what I'd expect from an AM signal. My circuit is from the datasheet example, and plenty of entries online allude to using this circuit, I can't get it to work. This is the second AM arrangement I've tried, the first with a transistor and I got similar rubbish results. I am clearly missing something, but after nearly 8 hours of searching I can't find the issue and it's driving me nuts!

If anyone has experience with this IC, please can you take a look?

Attached is the spice simulation (LT spice - I haven't used this package before, so could be an error there), also the green trace is the output. Input conditions are labelled on the schematic.

Any pointers / ideas really appreciated.

Thanks
Pete

 

[crutschow]

It looks like there is 5V offset on the input signals.
Set that to 0v.

 

[Ramussons]

Power supply to pin 5 should be -ve, not +ve.

 

[crutschow]

Here's my LTspice simulation:
I removed the input signals' DC offset.

 

[Boxnut]

Sounds like connected improperly or wrong bias for linearity.
You can double check here:

AM Modulator and Demodulator with integrated AD633 - YouSpice

PSpice simulation of a cascade of AD633 in modulator configuration and the same integrated AD633 in demodulator configuration. Project Type: For-Credits Complexity: Simple Components number: 11-20 SPICE software: PSpice Software version: 9.2+ Full software version nedeed : Yes Screenshots...

www.youspice.com

 

[atferrari]

Please verify the actual polarity on pins 5 and 8. Use a DMM for that.