oscillator rectification

[neptune]

so i want to rectify an oscillators oscillating voltage into DC.
i have used wein bridge oscillator , how do i achieve full wave rectification.
i am posting my simulation here it is half wave rectification how do i make it full wave.

 

[crutschow]

Use an op amp configured as a precision rectifier.

 

[ericgibbs]

hi neptune,
A Wien oscillator usually gives out a fairly 'constant' amplitude, due to the nature of its design.

Why would you want to rectify a steady amplitude sine wave.???

 

[carbonzit]

so i want to rectify an oscillators oscillating voltage into DC.
i have used wein bridge oscillator , how do i achieve full wave rectification.

I guess I also have to ask "Why?"

i am posting my simulation here it is half wave rectification how do i make it full wave.

Your .asc file seems to have some problems (missing op amp for one).

 

[ericgibbs]

hi neptune.

This FW rectifier is one option, I have used a voltage source for the sine wave in order to speed up the simulation.

Note: On the Wien I have set the IC of vp at 0.5V in order to kick start the osc, save me some sim time.

 

[neptune]

precision rectifier is not working. see

 

[ericgibbs]

precision rectifier is not working. see

Hi,
You missed off the.IC for a fast start, it works for me, use my settings.

EDIT:
Spotted an error in your circuit, the diode on the rectifier is wired wrong

 

[neptune]

hey man your precision rectifiier is giving too much low voltage at the output. (for 4V of peak to peak output is only few 500mV )
if we compare it to diode half wave rectifier it is giving far more high output (for 8V of pk tp pk output is 3.14V)
plus components used are costly.

 

[ericgibbs]

hey man your precision rectifiier is giving too much low voltage at the output. (for 4V of peak to peak output is only few 500mV )
if we compare it to diode half wave rectifier it is giving far more high output (for 8V of pk tp pk output is 3.14V)
plus components used are costly.

LOOK at the circuit I corrected for you, its a nominal +1Volt.

Your Wien output is ONLY 2Vppk when loaded by the rectifier OPA. If you full wave rectify a 2Vppk sine wave you get a 2Vpeak, if you now SMOOTH that with the cap, you will get a rough AVERAGE of +1Volt, which is what you see.!

 

[neptune]

I think you to should see the difference yourself
plus component count is far low and will take less space on board.
can you provide me full wave rectification through diodes only

 

[ericgibbs]

I think you to should see the difference yourself
plus component count is far low and will take less space on board.
can you provide me full wave rectification through diodes only

I would suggest that you do the maths for the full and half wave rectification of a sine wave signal having a 4Vpkk amplitude.
Smoothed and un-smoothed, with and without a load resistor.

 

[crutschow]

I think you to should see the difference yourself
plus component count is far low and will take less space on board.
can you provide me full wave rectification through diodes only

You can not full-wave rectify a signal from a grounded source to a grounded load with only diodes. A bridge-rectifier, for example, requires a floating source (or a floating load).

 

[neptune]

You can not full-wave rectify a signal from a grounded source to a grounded load with only diodes. A bridge-rectifier, for example, requires a floating source (or a floating load).

i have rectified a grounded source see

 

[carbonzit]

i have rectified a grounded source see

Sure, you half-wave rectified it. There's no way that lower diode is ever going to conduct anything.

Think about it.

 

[crutschow]

i have rectified a grounded source see

I see a half-wave rectifier. Perhaps you don't understand that a full-wave rectifier rectifies both the positive and negative halves of the waveform. Your circuit rectifies only the positive half. As CZ noted the bottom rectifier is connected to ground so how can it rectify the waveform?

 

[neptune]

oh my mistake !! so i cannot full wave rectify from a single source. both in real life and simulation world ?
but i want full rectification as its voltage output is more then half wave one, what should i do ?

 

[carbonzit]

Still curious: why are you generating a nice sine wave only to rectify it?

 

[crutschow]

oh my mistake !! so i cannot full wave rectify from a single source. both in real life and simulation world ?
but i want full rectification as its voltage output is more then half wave one, what should i do ?

You use a precision full-wave rectifier such as Figure 6 in this reference.

But you are in error about the voltage output. The peak voltage output of a full-wave rectifier is the same as a half-wave rectifier. The difference is that the full-wave ripple frequency is double that of a half-wave rectifier so the ripple voltage is less for a given filter value if you filter the voltage to get DC.

 

[neptune]

wikipidea has given half wave rectifier Vdc=Vpeak/ pie
and full wave as Vdc = 2xVpeak/ pie
is there any other formula ?
so if i get same voltage from both half and full then what's the use of using full wave or precision rectifier !

 

[neptune]

Still curious: why are you generating a nice sine wave only to rectify it?

i want to use this oscillation to be rectified so that i can compare voltage level of two oscillaters , one is inside the circuit oscillating at predetermined freq. and other one is outside like a wire carrying AC , we dont know its voltage level.