Monostable Waveforms: Solutions & Resources

[Weaver]

Homework Statement

[/B]

Homework Equations

T = Time constant x ln [span/remainder]

The Attempt at a Solution

a)[/B] The trigger pulse must have a negative polarity and an amplitude greater than 1V. V+ is at 0V in the stable state. By using these conditions for a triggering pulses, it ensures that will drop V- below that of V+ and so causing the op amp output to switch low and enter the quasi-stable state

b) ***I am a little unsure for part b, but this is my attempt:***

c) ***I am unsure of span and remainder for part c but this is my attempt:***

Span= 15-(-15)
= 30
Remainder = 15-1
=14

T = (10x10³ + 1x10³ )(100 x 10^-9) x ln(30/14)
T = 838.35us

Recovery approximately completes in 5 Time constants
=> 5 ( (10x10³ + 1x10³ )(100 x 10^-9) )
= 5.5 msd) ***I am a little unsure for part d, but this is my attempt:***
If V_ref was -1V, the V- would always be below V+ and so cause the monostable to be constantly producing a pulse.

Or is it that the circuit will responds to positive triggering pulses?

I am not very familiar with the monostable circuit. I'd appreciate any help with this question or even a link to a resource that explains the monostable circuit better. All the examples I find online seem to be a different circuit. Thanks in advance

 

[scottdave]

You state that a negative 1 volt trigger will start it (correct), but that is not what your picture looks like. Why do you have 2 trigger spikes (pos and neg)?

Try reading this article. It describes circuit using logic gates and transistors, but the basic operation is similar (the way the feedback temporarily holds it in one state). https://www.electronics-tutorials.ws/waveforms/monostable.html

 

[Weaver]

You state that a negative 1 volt trigger will start it (correct), but that is not what your picture looks like. Why do you have 2 trigger spikes (pos and neg)?

Thanks Scott!

I wasn't sure about that. We had trigger like that in a lab session but now in hindsight that was to show the circuit only responded to negative spikes. There only needs to be negative spikes as the positive will do nothing, given V- will still be greater than V+.

Would the graph then look like this?

Thanks for the link as well

 

[rude man]

Cn't read your drawing very well but looks like your V⁺ jumps from 0 to -1V and then exponentiates back to 0. The -1V is wrong, it'd be bigger than that by a factor of at least 2 ...

Duration of output pulse?

Part (d)?