Hi,
I'm currently exploring monostable multivibrators using 2 transistors. I'd like to know how I should expect the circuit to behave.
The first question I have is:
The "on" time that the circuit will produce, is this a square wave or more like a sawtooth? I've done a circuit where I have an LED connected to the output and I can see the LED fade out. This contradicts the diagram shown on wikipedia (a square wave). Is this happening because something is wrong in my circuit? Or is this expected?
Question 2:
The "on" time is calculated with 0.7*R*C. But does this take into acount the fact that the transistor will be "off" before the capacitor is fully discharged? Because the transistor will probably be "off" when voltage drops below 3v or so on the base. My LED also will stop glowing way before the R*C time has passed if the forward voltage is not met. But if, as per question #1, the output should be a square wave, then this shouldn't be a problem.
Question 3:
I'm still not clear on how the circuit should behave if the the period of the input signal is smaller than the period defined by R*C. In my testing, it seems like the input needs to be low long enough to allow the capacitor to fully recharge. Otherwise, the next trigger is short because it looks like the capacitor was not full. But again, it might be an error in my circuit. Or is this expected?
I'm currently exploring monostable multivibrators using 2 transistors. I'd like to know how I should expect the circuit to behave.
The first question I have is:
The "on" time that the circuit will produce, is this a square wave or more like a sawtooth? I've done a circuit where I have an LED connected to the output and I can see the LED fade out. This contradicts the diagram shown on wikipedia (a square wave). Is this happening because something is wrong in my circuit? Or is this expected?
Question 2:
The "on" time is calculated with 0.7*R*C. But does this take into acount the fact that the transistor will be "off" before the capacitor is fully discharged? Because the transistor will probably be "off" when voltage drops below 3v or so on the base. My LED also will stop glowing way before the R*C time has passed if the forward voltage is not met. But if, as per question #1, the output should be a square wave, then this shouldn't be a problem.
Question 3:
I'm still not clear on how the circuit should behave if the the period of the input signal is smaller than the period defined by R*C. In my testing, it seems like the input needs to be low long enough to allow the capacitor to fully recharge. Otherwise, the next trigger is short because it looks like the capacitor was not full. But again, it might be an error in my circuit. Or is this expected?