http://www.electronics-tutorials.ws/waveforms/monostable.html
The text underneath "Monostable Multivibrator Circuit" states, in para 2,
"If a negative trigger pulse is now applied at the input, the fast decaying edge of the pulse will pass straight through capacitor, C1 to the base of transistor, TR1 via the blocking diode turning it “ON”. The collector of TR1 which was previously at Vcc drops quickly to below zero volts effectively giving capacitor CT a reverse charge of -0.7v across its plates"
I'm having real difficulty understanding this. Please help and explain in layman terms ....
1.If a -ve voltage is applied to the input pin, then how does a -ve current pass through what would be a reverse biased diode given the anode is now -ve? The diaode is forward biased when +ve from R4/C1 through to TR1b. So how does a -ve current flow in that direction to effect a reverse charge at Ct
2. C1 is 100nf so what effect does this have, other than to smooth out the pulse ?
3. How does Ct get a reverse charge of -0.7v because R1 and R5 are connected to TRb and not TR1b where the -ve charge is.
Ive set this up in falstad circuit applet and applied -5v to the input and it does seem to work as described, but I just cant get my head around how??
Thank you in advance
(we all learned somewhere/somehow !)
The text underneath "Monostable Multivibrator Circuit" states, in para 2,
"If a negative trigger pulse is now applied at the input, the fast decaying edge of the pulse will pass straight through capacitor, C1 to the base of transistor, TR1 via the blocking diode turning it “ON”. The collector of TR1 which was previously at Vcc drops quickly to below zero volts effectively giving capacitor CT a reverse charge of -0.7v across its plates"
I'm having real difficulty understanding this. Please help and explain in layman terms ....
1.If a -ve voltage is applied to the input pin, then how does a -ve current pass through what would be a reverse biased diode given the anode is now -ve? The diaode is forward biased when +ve from R4/C1 through to TR1b. So how does a -ve current flow in that direction to effect a reverse charge at Ct
2. C1 is 100nf so what effect does this have, other than to smooth out the pulse ?
3. How does Ct get a reverse charge of -0.7v because R1 and R5 are connected to TRb and not TR1b where the -ve charge is.
Ive set this up in falstad circuit applet and applied -5v to the input and it does seem to work as described, but I just cant get my head around how??
Thank you in advance
(we all learned somewhere/somehow !)
Last edited: