K
Kingcosmos
- Jan 1, 1970
- 0
I am looking at the IVC102 from Texas Instruments, specifically the
first page:
http://focus.ti.com/lit/ds/symlink/ivc102.pdf
A colleague of mine is testing it under two conditions with pin 2:
floating and shorted to ground. Here is how I see it working:
With switch 1 open the summing junction of the integrator is not
connected externally (assuming ideal switch) so it does not matter if
pin 2 is floating or grounded in this case. If switch 2 is closed then
that shorts the feedback capacitors and you basically have a voltage
follower. I would expect to see the offset voltage on the output.
If switch 2 is open then I say the output will saturate to one of the
rails because of the input bias current (+/-) will charge the feedback
capacitors.
If switch 1 is closed and pin 2 floats then the above should happen as
well.
If switch 1 is closed and pin 2 is shorted to ground while switch 2 is
closed then the output voltage should be close to 0V. I see the output
and summing junction shorted to ground. In this case I can also see
lots of current draw because of that fact: the output is shorted to the
summing junction shich is shorted to ground by virtue of both switches
being closed and pin 2 connected to ground.
If switch 1 is closed, pin 2 is shorted to ground, but switch 2 is open
I still see a ~ 0V on the ouput because the summing junction is shorted
to ground. I don't see the input bias current charging the cap here.
My colleague does not see the last scenario (SW1 closed, pin 2 ground,
SW2 open) and he has not confirmed the other scenarios yet. He says
he sees a saturation voltage when switch 1 is closed, pin 2 grounded,
and switch 2 is open.
Am I all wet or can I say "Check your connections and logic voltages!"
first page:
http://focus.ti.com/lit/ds/symlink/ivc102.pdf
A colleague of mine is testing it under two conditions with pin 2:
floating and shorted to ground. Here is how I see it working:
With switch 1 open the summing junction of the integrator is not
connected externally (assuming ideal switch) so it does not matter if
pin 2 is floating or grounded in this case. If switch 2 is closed then
that shorts the feedback capacitors and you basically have a voltage
follower. I would expect to see the offset voltage on the output.
If switch 2 is open then I say the output will saturate to one of the
rails because of the input bias current (+/-) will charge the feedback
capacitors.
If switch 1 is closed and pin 2 floats then the above should happen as
well.
If switch 1 is closed and pin 2 is shorted to ground while switch 2 is
closed then the output voltage should be close to 0V. I see the output
and summing junction shorted to ground. In this case I can also see
lots of current draw because of that fact: the output is shorted to the
summing junction shich is shorted to ground by virtue of both switches
being closed and pin 2 connected to ground.
If switch 1 is closed, pin 2 is shorted to ground, but switch 2 is open
I still see a ~ 0V on the ouput because the summing junction is shorted
to ground. I don't see the input bias current charging the cap here.
My colleague does not see the last scenario (SW1 closed, pin 2 ground,
SW2 open) and he has not confirmed the other scenarios yet. He says
he sees a saturation voltage when switch 1 is closed, pin 2 grounded,
and switch 2 is open.
Am I all wet or can I say "Check your connections and logic voltages!"