In the middle of a project and its time for some fresh ideas.
The basic idea, is I am trying to delay a 80 mhz, 50% duty cycle, square wave. The amplitude of this signal is -.8V to gnd, which is what the output needs to be as well. The delay is desired to be variable between 50 picoseconds to 1 nanosecond.
My first prototype is shown in the schematic attached. The circuit turns a SN65LVDS2 into a high speed comparator, then the output is clamped with a signal diode to -.8V. The input has about 5pF gate capacitance. By using a 1K precision multi-turn pot, I hoped to get the desired delay at the non-inverting terminal of the line receiver (op-amp).
This is the basic schematic, I have installed a 50ohm terminating resistor at the input to impedance match the output of the pulse source.
I have a terrible problem with output attenuation at 80mhz, as well as some pretty nasty sidelobes. Again, this is unterminated (running the signal directly into the scope).
My RF foo is not particularly well groomed, so I'm very interested in suggestions to clean such a circuit up, or even a different methodology to explore.
Line Receiver Datasheet: http://www.ti.com/lit/ds/symlink/sn65lvds2.pdf
The basic idea, is I am trying to delay a 80 mhz, 50% duty cycle, square wave. The amplitude of this signal is -.8V to gnd, which is what the output needs to be as well. The delay is desired to be variable between 50 picoseconds to 1 nanosecond.
My first prototype is shown in the schematic attached. The circuit turns a SN65LVDS2 into a high speed comparator, then the output is clamped with a signal diode to -.8V. The input has about 5pF gate capacitance. By using a 1K precision multi-turn pot, I hoped to get the desired delay at the non-inverting terminal of the line receiver (op-amp).
This is the basic schematic, I have installed a 50ohm terminating resistor at the input to impedance match the output of the pulse source.
I have a terrible problem with output attenuation at 80mhz, as well as some pretty nasty sidelobes. Again, this is unterminated (running the signal directly into the scope).
My RF foo is not particularly well groomed, so I'm very interested in suggestions to clean such a circuit up, or even a different methodology to explore.
Line Receiver Datasheet: http://www.ti.com/lit/ds/symlink/sn65lvds2.pdf
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