desing of 6V to 5V AC circuit

[quris_terris]

i have 6V AC and i want 5V AC . plz tell me the circuit for taking 5V ac at output and input is 6V ac. i m giving this 5V Ac to an analog to digital conerter circuit .
i m taking 6V AC from 220V to 6V transformer. so plz tell me that how I got 5V ac for an ADC input so that the current is as much as ADC need

 

[olemp]

divide 6v ac with a basic resistive divider....
and connect the divided voltage to an opamp buffer...
you have to supply the opamp + and - voltages...

 

[usernam]

Why is a buffer needed here?
And what happens when the AC voltage goes negative. The current will then flow into the power supply. Wouldn't that cause some sort of power quality problems??

 

[pinkmouse]

Are you talking about powering the circuit with this 5V, or using it as an input to the ADC?

If this is for a power supply that needs 5VAC, then you should be OK feeding it the 6VAC you get from the traffo, as it will have internal rectification and regulation.

If you're using it as an input to the ADC, then a simple resistive divider will work.

 

[olemp]

if you are using that ac voltage just for your adc (not for supplying your devices)
probably it would't cause any problem....
and buffer for protect the shape of the divided voltage. in that case we don't consume current from resistors. so it prevents adc reading errors. also helpful when divided ac voltage exeeds 5v. in that case opamp clamps the output voltage to its own supply voltage.that protects adc input...

actually reading ac voltage with adc is not good idea...probably it would be more easy to rectifing and reading.....
also you can make a zero detect circuit to understand which alternate you are reading.....

and i did a small simulation with pspice: