I have a circuit of low pass filter. the input is 0 to 2.5 Volt. i need the output is 1 volt as DC signal. and I need the values of the R1, R2, R3 and C1. How much should be?
Average value of the input voltage is 0.25*2.5V = 0.625 V, respectively you can't get more than this DC level without an amplifier. 1 V can't be achieved.
To be able to calculate a low pass time constant, it's necessary to specify input frequency and acceptable residual output ripple.
Average value of the input voltage is 0.25*2.5V = 0.625 V, respectively you can't get more than this DC level without an amplifier. 1 V can't be achieved.
To be able to calculate a low pass time constant, it's necessary to specify input frequency and acceptable residual output ripple.
1)DC voltage is average voltage not RMS value? The RMS value of an AC supply is the steady DC which would convert electrical energy into thermal energy at the same rate in a resistance. So if we had at the output a resistance, why use average instead of RMS value? DC = average? RMS acts like beeing DC voltage too...
2)"About the ripple": Is not the output a square wave too? If there is any ripple, give me R and C values for a simple RC low pass filter to simulate it (not because I do not believe you, because I can not find R and C values to see that ripple at the output).
if I change the duty cycle to 75%. what will be the average value of the input?
2)"About the ripple": Is not the output a square wave too? If there is any ripple, give me R and C values for a simple RC low pass filter to simulate it (not because I do not believe you, because I can not find R and C values to see that ripple at the output).
In absence of C1, the output will be a square wave with the amplitude and source impedance changed. When you insert C1, it will integrate the voltage and the output will look more like triangular wave (depends on the value of C1 and the input frequency). With very large value of C1 and with a high enough frequency, you will get a stable DC value.
I hope this simulation is not cheating (in regard to the exercise questions, that is).
It answers several questions in this thread. It demonstrates behavior of RC time constant=1, with a frequency of 1 Hz.
1 Hz square wave
1 F
1 ohm
By some mathematical quirk, the capacitor points out the definition of the RC time constant. It reaches 63% of applied voltage after one time constant.
The full transfer function of the filter showed by the OP in post #1 is this one:
Regarding the term pointed with the arrow, to make it value "1" so then acts like the simple RC low pass filter, it is needed high R2 and low R1 which then changes the time constant etc..
My question is: Is not better to use the simple RC low pass filter rather than the other one?