I have an AC input of 0-5V that i need to go from -2.5 to 2.5V. this will then go through an op amp and then trough a push pull amplifier configuration. I just cant seem to find a value for the capacitor that will work, so if someone could explain where im going wrong that would be greatly appreciated. The input frequency is 1Hz.

 

Hi, you need a resistor from the + I put of the opamp to find to bias the opamp input.

 

+ I put should read + input of the opamp. Try 10k for starters.

 

hi 222,
A 1n0 input cap for 1Hz is much too low a value.
Try a 1uF.
E

 

hi brian,
Is this a College/Homework assignment project.?
E

 

yes i just couldnt find any formulas for the problem. i think i got it working fairly well at 10u and 100k

 

I have an AC input of 0-5V that i need to go from -2.5 to 2.5V. this will then go through an op amp and then trough a push pull amplifier configuration. I just cant seem to find a value for the capacitor that will work, so if someone could explain where im going wrong that would be greatly appreciated. The input frequency is 1Hz.
View attachment 224842

C1 Needs to be a Lot Bigger, at 1Hz

yes i just couldnt find any formulas for the problem. i think i got it working fairly well at 10u and 100k

The capacitive reactance of the capactor in Ohms (Xc) is 1/(2*pi*F*C). Any capacitor will do DC blocking but to allow 1Hz to pass a 10uF would approximate a 16k Ohms impedance.

 

to allow 1Hz to pass a 10uF would approximate a 16k Ohms impedance.

The signal will be reduced by 3dB (.707) at 1Hz with those values.
A value of 10μF and 50k will reduce the amplitude about 0.4dB (.95) at 1Hz.

 

You still need DC bias on the input of the op-amp.
The input resistance of TL072 is 10^12Ω.

 

You still need DC bias on the input of the op-amp.
The input resistance of TL072 is 10^12Ω.

Already mentioned in reply #2.

 

1Hz is almost DC. The signal generator is grounded so if it has no output coupling capacitor then its DC output is 0V and the input capacitor feeding the opamp is not needed.

 

The signal will be reduced by 3dB (.707) at 1Hz with those values.
A value of 10μF and 50k will reduce the amplitude about 0.4dB (.95) at 1Hz.

The values were just based on his values stated as acceptable in post #6, i missed the 100k resistor