hi all, i want to ask u guys about something very strange happen in an analog multiplier IC , i have an anlog multiplier IC it works as a modulator has two input signal the carrier signal and the information signal and the output is modulation of them , when i connected the output to an oscilloscope i did't see any thing just random noise , but the strange thing when i accidentally connected the oscilloscope prob to the Vcc of the multiplier (+5v) the signal which appeared on the oscilloscope is the carrier signal !!! with the exact carrier frequency, how the carrier signal came out from the Vcc terminal or may be the IC is damaged ? (btw the IC has +5v ,-5v and ground pins) , i need an explanation plz

 

We will need a schematic before we can explain this failure mode of an integrated circuit.

Please.

 

Will that circuit show some fairly large capacitors across the supply rails and ground? Lack of adequate supply decoupling capacitors could lead to poor performance, with significant signal amplitudes appearing on the supplies. See link: http://forum.allaboutcircuits.com/showthread.php?t=45583

 

thanx for replying, i read the link and i think i connected the IC wrong because i did't use any external component for it, plz take a fast look on the circuit i used to connect the IC , in the datasheet page 11, but i think i should use the one in page 10...also do u think the IC is damaged?

http://www.analog.com/static/imported-files/data_sheets/AD835.pdf

 

The IC may be damaged, there is only one way to tell for sure.

Connect it correctly, with decoupling capacitors, and probe the output again.

If you are getting proper output, then you are likely fine.

Without seeing how you connected it incorrectly, we cant tell if you supplied power to a protected or unprotected output pin.

 

@retched thanx for replying, i just want to know one thing if the circuit i should use is the one in page 10 , so what is the ciruit in page 11 for ??

 

From the datasheet, page 11:

MULTIPLIER CONNECTIONS
Figure 20 shows the basic connections for multiplication. The
inputs are often single sided, in which case the X2 and Y2 inputs
are normally grounded. Note that by assigning Pin 7 (X2) and
Pin 2 (Y2), respectively, to these (inverting) inputs, an extra
measure of isolation between inputs and output is provided.
The X and Y inputs may be reversed to achieve some desired
overall sign with inputs of a particular polarity, or they may be
driven fully differentially.

Power supply decoupling and careful board layout are always
important in applying wideband circuits. The decoupling
recommendations shown in Figure 20 should be followed
closely. In Figure 21, Figure 23, and Figure 24, these power
supply decoupling components are omitted for clarity but should
be used wherever optimal performance with high speed inputs
is required.

This is why you saw the signal on the +5v line; you did not use the decoupling capacitors that are shown in figure 20.

You MUST READ THE DATASHEET and follow the guidelines while using the product, or you will have poor results.

You must use the decoupling capacitors as shown in Figure 20. As far as which figure to use, choose one - but make certain to use the capacitors.

 

@SgtWookie , man u my hero !!! u have an answer for every problem i face