Hi,
I came across a problem yesterday, and I wonder how one does to find the good answer.
Using a voltage divider configuration, I took a 9V battery to provide a logical 5V (Vcc) to a Schmidt trigger IC.
But to calculate the good value of R1 to pick for the voltage divider, I needed to know the equivalent resistance of the IC acting as R2 in the VD. (real part of the impedance, because I use a DC source).
Nevertheless, this IC is not a passive piece of hardware, so as long as it is not "polarised", not giving the IC its Vcc, a physical ohmic measurement will show a huge resistance value.
So here it is:
Question #1: How does one measure the equivalent resistance of a chip if you don't have the proper source voltage to "polarize" it, and therefore see its operating equivalent resistance?
Question #2: Would this information be provided on the datasheet...? If so, what is the usual name given to this spec..? I didn't investigate yet. Maybe I should.
Question #3: In simulation, should I polarise the IC properly, then measure its resistance and then proceed with my calculations to find R1 or again... use the datasheet?
Thanks,
zeta_no
p.s: I ended up making R2 with the IC in parrallel with a small resistance (around 100 Ohm). Therefore, I minimized the effect of the IC load, what ever its value, on the voltage divider. Nevertheless, this way I didn't get a sharp 5V.
p.s.2: Sorry for the length...
I came across a problem yesterday, and I wonder how one does to find the good answer.
Using a voltage divider configuration, I took a 9V battery to provide a logical 5V (Vcc) to a Schmidt trigger IC.
But to calculate the good value of R1 to pick for the voltage divider, I needed to know the equivalent resistance of the IC acting as R2 in the VD. (real part of the impedance, because I use a DC source).
Nevertheless, this IC is not a passive piece of hardware, so as long as it is not "polarised", not giving the IC its Vcc, a physical ohmic measurement will show a huge resistance value.
So here it is:
Question #1: How does one measure the equivalent resistance of a chip if you don't have the proper source voltage to "polarize" it, and therefore see its operating equivalent resistance?
Question #2: Would this information be provided on the datasheet...? If so, what is the usual name given to this spec..? I didn't investigate yet. Maybe I should.
Question #3: In simulation, should I polarise the IC properly, then measure its resistance and then proceed with my calculations to find R1 or again... use the datasheet?
Thanks,
zeta_no
p.s: I ended up making R2 with the IC in parrallel with a small resistance (around 100 Ohm). Therefore, I minimized the effect of the IC load, what ever its value, on the voltage divider. Nevertheless, this way I didn't get a sharp 5V.
p.s.2: Sorry for the length...