LC Tank Circuts have me baffled

[Dean]

I am not smart enough to understand how the common ' tank circut ' works as
used in LC oscillators. The current first flows through the cap then through
the inductor because caps allow immediate current flow and inductors resist
it I know, but I'm buggered if I'll ever understand how the transistor
switching circut 'knows' when to kick it the other way.

Many of you will in aus.electronics will have designed hundreds of such
circuts and understand precisly how they work. I admire you !

I hope the light bulb above my head starts attracting moths soon.

Dean.

 

[Alan Rutlidge]

I am not smart enough to understand how the common ' tank circut ' works as
used in LC oscillators. The current first flows through the cap then
through the inductor because caps allow immediate current flow and
inductors resist it I know, but I'm buggered if I'll ever understand how
the transistor switching circut 'knows' when to kick it the other way.

Many of you will in aus.electronics will have designed hundreds of such
circuts and understand precisly how they work. I admire you !

I hope the light bulb above my head starts attracting moths soon.

Dean.

Keep that light on and sooner or later you'll attract Phil Allison's
attention.
Although I'm not sure if that's a good idea or not.

Do a Google search on "tank circuit" or "LC circuits" for more info.
Better still go to your local library and borrow a good text book or two on
the subject.

Cheers,
Alan

 

[Ed \(\)]

XC=XL
the key is in the Z

 

[Craig Hart]

You have it the wrong way around.

A regulation LC tank circuit is tuned to resonate with the frequency of the
drive transistor's switching.

The switching transistor is itself driven from another ("earlier") part of
the circuit which sets the actual required frequency - the tank circuit has
no influence on the transistor's switching frequency what so ever.

Craig

 

[Ed \(\)]

you dont have this bit right
a frequency multiplier stage works with the tank tuned to 147MHz and the
drive at 49MHz
the tank will store energy and ring at 147MHz, and gets topped up every
3 cycles

: You have it the wrong way around.
:
: A regulation LC tank circuit is tuned to resonate with the frequency
of the
: drive transistor's switching.
:

 

[Craig Hart]

who said anything about frequency multiplication??

Tank circuits can be used for that purpose, but they have plenty of more
common uses at fundamental too. The OP doesn't mention frequency
multiplication in his question......

Where did you get 49MHz and 147MHz from, anyhow...? That's not the only
frequency a multiplier can work at, after all...

 

[Ed \(\)]

who didn't say anything about frequency multiplication??
and its useful to consider real freqs, any freq will do.

the example disproves that switching has to be done at the tank freq.

why, you have somthing to add??

: who said anything about frequency multiplication??
:
: Tank circuits can be used for that purpose, but they have plenty of
more
: common uses at fundamental too. The OP doesn't mention frequency
: multiplication in his question......
:
: Where did you get 49MHz and 147MHz from, anyhow...? That's not the
only
: frequency a multiplier can work at, after all...
:
:
:
:
: : > you dont have this bit right
: > a frequency multiplier stage works with the tank tuned to 147MHz and
the
: > drive at 49MHz
: > the tank will store energy and ring at 147MHz, and gets topped up
every
: > 3 cycles
: >
: > : You have it the wrong way around.
: > :
: > : A regulation LC tank circuit is tuned to resonate with the
frequency
: > of the
: > : drive transistor's switching.
: > :
: >
:
: