DC-offset schematics? anyone?

[jean-charles maillet]

>hi guys, i'm doing something with an LFO that needs to be DC-offset cuz it's
>not working with the LFO i have now (+/-2.5v) and i need to offset it to
>zero to +5v. anyone got any simple schemos to a module like this? or even a
>complicated one?

you can use a simple current source driving a follower circuit (buffering
your source node) and a diode or resistor string between the follower and
the current source.  Several variants of this can be found in linear
circuit and op-amp design texts.

jc

                        +Vcc
                          |
                         /
node to be shifted -----|    npn
                         \e
                          |
                          |
                          D
                          |
                          D
                          |
                          D
                          |
                          D
                          |
                          D
                          |___________ shifter output
                         /
    I source bias  -----|    npn
                         \e
                          |
                        +Vcc

the amount of current sunk by the source will determine the amount of
voltage shift depending on the diode (or resistor) characteristics.  If you
use a resistor you lose drive if the value is high, diodes are used for
high drive.  The transistors can be 2n3904's.  This can work on single
supply circuits too but you may run out of headroom depending on the ampunt
of shift desired and supply voltage.

Ooops sorry, you want a +2.5v shift ... flip this circuit vertically and
use pnp's ... 2n3906's I think ...

jc