XR-8038A function generator IC datasheet question.

[boylesg]

What is Vsup? There is no explanation of it any where in the datasheet.
If Vcc is +9V and Vee is -9V then what voltages should Vin be between?

 

[KlausST]

Hi,

please post a link to the datasheet.

Klaus

 

[danadakk]

http://electronic-engineering.ch/radiocontrol/datasheets/xr8038.pdf

Regards, Dana.

 

[boylesg]

View attachment 178229

http://electronic-engineering.ch/radiocontrol/datasheets/xr8038.pdf

Regards, Dana.

Is Vsup = Vcc - Vee?
In my case that would be about 16.8V since I am using 2 x 9V NiMH batteries in series with GND in the middle. Which output about 8.4V or so.

--- Updated Aug 26, 2022 ---

And another question re this....
Would 100nF and 10k be OK for that cap and resistor on pins 7 and 8?

 

[danadakk]

Is Vsup = Vcc - Vee?
In my case that would be about 16.8V since I am using 2 x 9V NiMH batteries in series with GND in the middle. Which output about 8.4V or so.

--- Updated Aug 26, 2022 ---

And another question re this....
Would 100nF and 10k be OK for that cap and resistor on pins 7 and 8?

View attachment 178230

Yes Vsup = Vcc - Vee

The R on FMB1 allowed to go to 1 Mohm. C, not sure, as there is no
data on Zin of the FMS1 pin, but try your val out,m should be fine I
think.


Regards, Dana.

 

[KlausST]

Hi,

I´d say the C (in combination with the R) determines the lower cutoff frequency for the modulation.
Or the other way round: calculate C by using R and fc

Klaus

 

[danadakk]

I would say its more compicated than just simple RC calculation of
externals based on whats connected to pins 7 and 8 :

However looks like we can "swamp" out the effective internal Z's with large R. assuming
Rextb is small relative to the R on pin 8.


Regards, Dana.

 

[boylesg]

Hi,

I´d say the C (in combination with the R) determines the lower cutoff frequency for the modulation.
Or the other way round: calculate C by using R and fc

Klaus

So I take it that capacitor and resistor forms a low pass filter then? Which I would have to refresh my memory on.

 

[KlausST]

Hi,

Exernal R has to be added to internal R of pin 7 (8k) to get the total R for fc calculation.
(ignoring Pin8 current)

Klaus

 

[danadakk]

A LPF would help remove noise and unwanted changes to your control V input
signal. So it would aid in making your modulation input, your control signal, free
of any unwanted deviations from what you would like.

Regards, Dana.

 

[KlausST]

Hi,

I agree that a low pass filter attenuates noise (and jitter)

But the R-C at the FM input of post#1 form a HIGH pass filter.

Klaus

 

[danadakk]

Or does it do nothing other than AC couple modulation signal, given that
cap directly connects to a voltage control bias point in internal circuit ? The R
is for Zin control.

https://www.mit.edu/~6.331/icl8038data.pdf

Regards, Dana.

 

[KlausST]

Hi

Or does it do nothing other than AC couple modulation signal,

Yes, AC coupling usually is done by using an HPF.

Klaus

 

[danadakk]

Practically speaking are we DC coupled when we use a bulk cap, like electrolytic, or
any cap for that matter, with their leakage issues ? Eg. we cant actually build a true
HPF....Just asking for a friend.


Regards, Dana.

 

[KlausST]

Hi,

Yes, if you are focussed on the leakage current of a capacitor ... rather than it´s function as a capacitor.

Klaus

 

[danadakk]

Of course we care about non perfect components, like caps. Their ESR,
for some (ceramics) wild dependency on V, or T dependence, mechanical
microphonics.....to name a few. Should we be worried about muon and
neutrino interaction in dielectrics ? Gravitational waves, all should be
focused on.

Buts its fascinating, is there such a thing as a realizable HPF ? I am having
my doubts.


Regards, Dana.

 

[KlausST]

Hi,

I guess you´re getting off topic.
You are free to start your new thread for discussions of non perfect parts and whether a HPF realizable.

Please here post topic related content only.

Klaus