- #1
Jdo300
- 554
- 5
Hello All,
I'm working on designing a simple circuit that takes a square wave clock input and converts it to a sine wave using a Johnson Counter, an R2R ladder and an output filter capacitor (see the below link for reference):
http://books.google.com/books?id=rZ... sine wave generator johnson counter&pg=PA360
I want to be able to use this circuit in a pretty dynamic range 1Hz to 1MHz and this circuit appears to be the simplest way to go about it (aside from programming a microcontroller and using a DDS IC with it). This circuit gives me the ability to simply clock it with a function generator to set the output frequency.
However, there is one problem; the output filter circuit as pictured in the schematic is only designed to work in one narrow frequency range. I would like to make it work through the whole input range of 1Hz to 1Mhz without needing to manually switch in and out RC values to keep the filter in the right range. So I was thinking that if I could just design the filter for somewhere in the low range, and then add an AGC amplifier to the circuit, that the amp could keep the output amplitude constant as the frequency is increased (and the resulting output sine wave decreases).
I know that AGC amplifiers are used all the time in audio equipment and I'm currently trying to do some research to see what kinds of ICs are available out there. Has anyone here ever worked with these types of amplifiers? If so, I would appreciate any suggestions people may have :-)
Thanks,
Jason O
I'm working on designing a simple circuit that takes a square wave clock input and converts it to a sine wave using a Johnson Counter, an R2R ladder and an output filter capacitor (see the below link for reference):
http://books.google.com/books?id=rZ... sine wave generator johnson counter&pg=PA360
I want to be able to use this circuit in a pretty dynamic range 1Hz to 1MHz and this circuit appears to be the simplest way to go about it (aside from programming a microcontroller and using a DDS IC with it). This circuit gives me the ability to simply clock it with a function generator to set the output frequency.
However, there is one problem; the output filter circuit as pictured in the schematic is only designed to work in one narrow frequency range. I would like to make it work through the whole input range of 1Hz to 1Mhz without needing to manually switch in and out RC values to keep the filter in the right range. So I was thinking that if I could just design the filter for somewhere in the low range, and then add an AGC amplifier to the circuit, that the amp could keep the output amplitude constant as the frequency is increased (and the resulting output sine wave decreases).
I know that AGC amplifiers are used all the time in audio equipment and I'm currently trying to do some research to see what kinds of ICs are available out there. Has anyone here ever worked with these types of amplifiers? If so, I would appreciate any suggestions people may have :-)
Thanks,
Jason O