pannaguma
Junior Member level 1
Hi guys,
i am working on a comb generator as part of a summer project.
I intend to sweep the tuning voltage range of the VCO, with a frequency which corresponds to the comb spacing.
Now I am using a 555 circuit in astable mode to generate the ramp signal.
**broken link removed**
The problem is that i need to add an offset voltage to the above ramp.
i thought of two solutions to this:
1>use two 741s, each in inverting mode with the first one acting as a summing amplifier.
OR
2>use a zener diode of required offset voltage to 'prop up' the voltage obtained at the capacitor.
But neither seems to work. In the first case there is a lot of distortion due to the capacitor not discharging quickly enough, and the ramp ends up looking like a triangle wave.
In the second case, i figure though it will work in other circuits, in my case since i require only a 0.5V offset, to a ramp of 4V amplitude (ie, from 0.5-4.5V) in practice zener diodes of 0.5V breakdown voltages will impossible to obtain.
Any ideas how i can obtain the required signal?
Thanks for reading.
i am working on a comb generator as part of a summer project.
I intend to sweep the tuning voltage range of the VCO, with a frequency which corresponds to the comb spacing.
Now I am using a 555 circuit in astable mode to generate the ramp signal.
**broken link removed**
The problem is that i need to add an offset voltage to the above ramp.
i thought of two solutions to this:
1>use two 741s, each in inverting mode with the first one acting as a summing amplifier.
OR
2>use a zener diode of required offset voltage to 'prop up' the voltage obtained at the capacitor.
But neither seems to work. In the first case there is a lot of distortion due to the capacitor not discharging quickly enough, and the ramp ends up looking like a triangle wave.
In the second case, i figure though it will work in other circuits, in my case since i require only a 0.5V offset, to a ramp of 4V amplitude (ie, from 0.5-4.5V) in practice zener diodes of 0.5V breakdown voltages will impossible to obtain.
Any ideas how i can obtain the required signal?
Thanks for reading.
