Hammerhead question

[Kev]

Hi,
I'm working on a Hammerhead hybrid using a PIC for timing, settings input & display. I want to use a non-VCO audio option. I will need to chop the final amp ouput with the PIC. But I'm not completely sure what the chopping actually does. I suspect that it squares the amps output to provide a dynamic signal for the audio amp?
Also does anyone know of a bilateral switch other than a 4066 that has a lower on resistance with a bipolar supply?

Regards Kevin

[Carl]

Re: Hammerhead question

Yes, chopping converts the DC output of the integrator/amplifier into a square wave for audio. Yes, most chip companies (Analog Devices, TI, Maxim, etc) have super-low-resistance switches, although not necessarily pin-compatible with the 4016/4066. Why do you need lower resistance?

- Carl

[Kev]

Re: Hammerhead question

Hi Carl,
Thanks for the confirmation on this. I'll need to experiment with the duty cycle a bit. The reason I asked about the 4066 was a datasheet I was reading (it's at home so can't give you the make right now) gave a quite good on resistance of about 50 Ohm, but further down the sheet in another table, alluded to the transfer against signal voltage figures wherein R on had risen to 2k5 Ohms for a 1 volt signal. I was a bit lazy I guess in asking if anyone had come across a better switch, since I hate reading datasheets and often find that first page parameter values are eroded as one reads on and looks at the fine print.
Anyway I see that not all 4066's are created equal, so I'll continue to look around. It probably doesn't matter a great deal anyway since the integrator input is such a high resistance.
I see from figure 25 page 11 of the Hammerhead construction sheet that the response of that particular IC is OK.

Regards
Kevin