awmt102
Newbie level 4
Hi all,
I have been trying to create a circuit that has a very fast rise time (in the order of 10ns) but with a relatively slow fall time (prefereably as high as possible in the range 500ns to 4ms).
The reason for this is so that I can drive an RLC circuit with a positive going edge only (which needs to be fast) and for it to ignore the negative going edge (which can be achieved by making it very slow).
I have simulated a circuit that appears to achieve this very simply - a button drives a schmitt inverter. The output of the schmitt drives a fast opamp buffer and is tied to ground with a 100mH inductor. The opamp is running from a single supply.
In the simulation when the button is pressed it creates a low on the schmitt input which generates a fast rising edge (10ns) on the inductor. The voltage accross the inductor decays to zero in about 1ms. When the button is release the voltage accross the inductor goes negative very quickly and then decays to zero slowly. The opamp buffer clips out the negative going aspect so I get a nice fast rising edge and slow falling edge to drive my RLC circuit with. (See attached file for a schematic and waveform output - sorry for the proo quality but I had to redraw itin paint as i cannot get it from the my laptop to the internet computer at work!)
However when I build it I find that I get a fast rising edge but it decays to about 2V the stays at that level.
Does anyone know why the output never drops to 0V??? Or can anyone suggest another way to achieve what I want?
I have been trying to create a circuit that has a very fast rise time (in the order of 10ns) but with a relatively slow fall time (prefereably as high as possible in the range 500ns to 4ms).
The reason for this is so that I can drive an RLC circuit with a positive going edge only (which needs to be fast) and for it to ignore the negative going edge (which can be achieved by making it very slow).
I have simulated a circuit that appears to achieve this very simply - a button drives a schmitt inverter. The output of the schmitt drives a fast opamp buffer and is tied to ground with a 100mH inductor. The opamp is running from a single supply.
In the simulation when the button is pressed it creates a low on the schmitt input which generates a fast rising edge (10ns) on the inductor. The voltage accross the inductor decays to zero in about 1ms. When the button is release the voltage accross the inductor goes negative very quickly and then decays to zero slowly. The opamp buffer clips out the negative going aspect so I get a nice fast rising edge and slow falling edge to drive my RLC circuit with. (See attached file for a schematic and waveform output - sorry for the proo quality but I had to redraw itin paint as i cannot get it from the my laptop to the internet computer at work!)
However when I build it I find that I get a fast rising edge but it decays to about 2V the stays at that level.
Does anyone know why the output never drops to 0V??? Or can anyone suggest another way to achieve what I want?