I am trying to test this circuit from below but I a not sure which kind of capacitor should I use and how should I use it.

My question begins here, as I found two contradictory schematics, one is from ST and the other is from On Semiconductor. Although ON seems 'clear' on what to connect and where, ST makes it seem dubious. See the pictures as a reference.

ST and ON Semiconductor datasheet for 4538

ST seems to point that pin 1 and pin 15 should be only tied to one end of the capacitor while the other should be connected to the resistor in series. But on the following page it seems to indicate the contrary, in other words that pin 1 and 15 by extension should be tied to GND. Am i missing something?

In order to clarify or settle any doubts i referred to ON Semiconductor which can be seen below in the same picture from above.

However they do not seem to 'clear' my doubts regarding the correct connection of the capacitor as i am not familiar with the notation or drawing of the capacitor with one curved end. Mind somebody explain this part?

Now the second part of my question and that it includes the first one as well is that I am trying to test out this circuit.

Oscillator circuit using gates

However once again I am not sure which way should that capacitor be connected, since what I want to try out are capacitors of let's say 1uF and beyond, those seem to come as polarized varieties, like aluminum or tantalum. Wikipedia article states tantalum have low leakage and that they are good for sample and hold circuits and applications where timing is not critical. Overall what type of capacitor is recommended for both circuits?. Because I am confused on the right connections as I dont want to destroy or damage any component I would like to get that clarification first.


The RCA and TI CD4538 datasheets I have show a terminal assignment diagram, with a note stating that pins 1, 8, and 15 are connected internally, so there is no need to ground 1 and 15 externally.

  • \$\begingroup\$ I see. Can you share a picture of the schematic you are referring to?. By the way this only addresses one part of the question. How about the other which i am confused and this is about the polarity markings in the picture from above and the way how it should be connected in the circuit (i'm referring also to the one below with gates 4011). That capacitor does is not polarized, can i use one which IS polarized?. If so how do i connect it correctly without any damage?. \$\endgroup\$ Nov 8 '16 at 20:09
  • \$\begingroup\$ Do a Google search for "CD4538B datasheet TI" \$\endgroup\$ Nov 8 '16 at 20:40
  • \$\begingroup\$ I did what you said but the datasheet you mention doesn't seem to clear out my doubts. Also this doesn't addresses the other problem, how should those capacitors be connected?. \$\endgroup\$ Nov 17 '16 at 17:45

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