[Menu]>[Electronic circuit beans collection]


Differentiation circuit




This circuit is used when getting the signal having to do with the pulse from the input signal of the square wave.

The circuit of this form is used to interrupt the relation having to do with the direct current among the circuits, too.(Direct current cut) In the case, the signal of the square wave causes the warp. Also, in case of the analog signal, the voltage which is output in the capacity of the capacitor changes. The influence comes out to the extent that the input signal is low-frequency.

The use example : Voltage change circuit of Car speed detection device and so on.


The photograph above is the one of the following condition.
F:50Hz
C
:0.22F
R
:10K-ohm





The electric charge begins to store up in capacitor(C) when the voltage is applied to the input. The electric current which flows into the capacitor as the electric charge is stored up decreases.
The electric current change which flows through the capacitor(C) and the resistor (R) is demanded by the following formula.
    i = (V/R)e-(t/CR)

    i:The electric current which changes in the time(A)
    V:The applied voltage(V)
    R:The resistance value(ohm)
    C:The capacitor value(F)
    e:The base of the natural logarithm(2.71828)
    t:The elapsed time after the charging beginning(sec)
    CR:The capacitive time constant (C x R)


The change of the voltage which appears in the both edges of the resistor (R) becomes the following formula.

iR = V[e-(t/CR)]

It is as follows when showing the formula above by the graph.