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Zener Diode in Circuit Diagram

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bigal_scorpio

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Hi to all,

Just wondered if anyone can tell me the reason that the Zener diode in the table below Fig.1 has the same value resistor for all the values of Zener's?

It seems to me that they have gone to the trouble of making a table for no good reason or is there an error somewhere, I mean whats the point of making an if then scenario when all the thens are the same? :confused:

Thanks for looking..........Al
 

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its being used as a crude voltage regulator. The supply coming in is 12V, but this chips takes a Vcc of 5V max
 
Zener query

Styx said:
its being used as a crude voltage regulator. The supply coming in is 12V, but this chips takes a Vcc of 5V max


Yeah, I get the voltage reg part, but why the table with the different Zener's and the same resistor values?

Is there a reason? :confused:

Al
 
ahh I see what you mean. Yer seems odd. Its like "whatever rail you are gonna run from, use a 82k resistor"

would of been easier just to say that
UNLESS typo in the datasheet
 
I guess it isn't any more silly than R2 in that circuit. :D
 
kchriste said:
I guess it isn't any more silly than R2 in that circuit. :D
R2 will discharge C1 all the way to ground (I know, it will never fully discharge) when the 12V supply is turned off. Without it, the last volt or so might take a while. Why that would matter is another question.
 
hi Al,
Unless I am having a 'senior moment' the R4 resistor isnt connected to the Zener???

It refers to the R/C timing for the Tone Gen ic.

R1 is the zener drive resistor.
 
I must be having a senior moment because the datasheet stated that the IC has max. operating current of 800mA.

A 1K+zener arrangement to provide 800mA to the IC?
 
eblc1388 said:
I must be having a senior moment because the datasheet stated that the IC has max. operating current of 800mA.

A 1K+zener arrangement to provide 800mA to the IC?

hi,

The operating current stated is for the full circuit Fig1 NOT the zener.

The R1/Z1 supplies the Tone Gen NOT the whole circuit....:p
 
Last edited:
ericgibbs said:
hi,
The operating current stated is for the full circuit Fig1 NOT the zener.

I have to re-read the datasheet once again just to be sure.

I bet to differ. It is clearly stated that at VCC=5V and in an arrangement as Fig.1 the operating current of the IC is 800mA max.

Obviously the datasheet is wrong.
 
eblc1388 said:
I have to re-read the datasheet once again just to be sure.

I bet to differ. It is clearly stated that at VCC=5V and in an arrangement as Fig.1 the operating current of the IC is 800mA max.

Obviously the datasheet is wrong.
I would bet good money that's a typo, and it is supposed to be 800uA. 4 watts dissipation in an 8 pin dip? More like a 6-color smoke generator than a 6-tone sound generator.
As you said, the datasheet is wrong.
 
The IC is a low current Cmos one. Its output current is only 5mA and the dalington transistors amplify it to a peak current of 10V/8 ohms= 1.25A. The duty-cycle reduces the entire circuit's average current to 800mA.
 
audioguru said:
The IC is a low current Cmos one. Its output current is only 5mA and the dalington transistors amplify it to a peak current of 10V/8 ohms= 1.25A. The duty-cycle reduces the entire circuit's average current to 800mA.
You're probably right. The current spec does say "(Referrence [sic] Fig.1)". Fig.1 is the entire schematic.
 
bigal_scorpio said:
the reason that the Zener diode in the table below Fig.1 has the same value resistor for all the values of Zener's?

I would think that the value of the zener depends on the supply voltage. The chip is rated from 2 to 5 volts and the zener is part of a crude regulator, the lower values would be for lower supply voltages to lessen the effect of supply on frequency. Bit of a naff setup...
 
Roff said:
You're probably right. The current spec does say "(Referrence [sic] Fig.1)". Fig.1 is the entire schematic.

morning Ron,
Thats the way I read it also, the 'circuit' current not the ic alone.

hi Gordz,
The R4 table relates to the ic oscillator, not the zener diode feed resistor.
The circuit shows a +12Vsupply., R1 and a Zener.

I think we all agree parts of the spec description are a little 'naff'.;)
 
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