PI-1 opt 1 INESTABILITY

[Serafin]

Hi. I buld the PI1 opt1 of carl but lose sensivility at few seconds in not autotrack mode you know why?


Thanks...Best regards

[Carl]

Re: PI-1 opt 1 INESTABILITY

If you take it out of autotrack, then any bias current from IC8b will eventually charge C19 an rail the gain stage. How long it will run OK, depends on the bias current, which is why I used a JFET-input opamp. But even these have a few nanoamps, and will only give 15-30 seconds of non-autotrack operation, plenty for most pinpointing. There are probably some CMOS-input opamps out there which could work well for several minutes.

- Carl