I have come across a design for an oscillator that, boiled down to its essentials, has a configuration like this:
,--- VCC | .-. | | 330 | | '-' | | .----UUU----o | | | | --- | --- | | o--- Output | | | 22k | | ___ | o---|___|---o | | | | | |/ '---------| |>
| | '--- GND
But I can't see how it's supposed to work. The series LC network from collector to base looks like it should be providing negative feedback rather than positive!
(The full circuit is shown below, in case it makes any difference. The frequency-determining capacitor is actually a pair of varicap diodes used for frequency control.)
,--- VCC | | C C C | | | .-. | | 330 | | 390p '-' | || | ,-----o----||-----UUU----o | | || | | V | | - | 47k | - | ___ | | o--- Output Control ---|___|----)-----o | | | 22k | | - ___ | | - ---|___|---o | ^ | | .-. | | | | | | | |/ 47k | | '------o---------| '-' |>
| | | | '------------------------o--- GND