Chopper

Mad Analogue Switch

This is an analogue switch on steroids. The concept came from a 60s chopper modulator circuit. It can be used as a VCO, a VCF, a waveshaper, ring modulator, analogue switch, LFO and VC gate generator....probably more. It can switch between two input signals with the actual input signals deciding when to switch, or the change can be VC or manually controlled. There is also a bi-directional switch as a separate circuit on the same PCB. this is functionally the same as the early Serge bi-di Router but uses a DG411 analogue switch rather than a 4007 to do the work.

From the Build Notes: http://www.sdiy.org/pinky/data/Chopper%20BUILD%20NOTES.pdf
What is the Chopper? The concept came from a 1975 paper titled – ‘A nonlinear modulator using delta principles’ by S.K. Mullick and K.R
Srivathsan.

The signal being passed thru the switch is also being sent to the comparator via a slew section and
used to decide when the switch will flip. The actual circuit is of course more complex than this.
The comparator can be set with a pot and then modulated with a CV. There are two gate outputs from the comparator,
when one is high the other is low. There is the switch output and the slewed output.

https://www.nonlinearcircuits.com/modules/chopper