Electronic apparatus for biological research electronicappara00dona Year: 1958 DIODE CIRCUITS From the point of view of regulation, then, there is an optimum value of C; the calculations involved in finding it are complicated, but fortunately the manufacturers of rectifying diodes are very helpful, in their pubHshed data, with recommendations on this point. Practical values range between 4 and 32 /^F. rvn Figure It is now evident why the full-wave system of power rectification is so much to be preferred. Diode conduction times occur twice as often {Figure ) so for a given load and c
Electronic apparatus for biological research electronicappara00dona Year: 1958 DIODE CIRCUITS From the point of view of regulation, then, there is an optimum value of C; the calculations involved in finding it are complicated, but fortunately the manufacturers of rectifying diodes are very helpful, in their pubHshed data, with recommendations on this point. Practical values range between 4 and 32 /^F. rvn Figure It is now evident why the full-wave system of power rectification is so much to be preferred. Diode conduction times occur twice as often {Figure ) so for a given load and capacitance the peak diode current is halved, thus regulation is improved. Alternatively, more capacitance can be used for the same regulation, thus reducing the ripple. Another important point is that the fundamental ripple frequency is doubled, which facilitates further smoothing. 1~ Peak to peak ripple Figure The ripple voltage may be estimated in the following way. Suppose all the diode current per cycle flows instantaneously, then the output waveform is triangular and the capacitance supphes load current for time T {Figure ). The rate of discharge for the capacitance is constant for all reasonable values of C and equal to IjC volts per second where / is the load current. For half- wave systems on 50 cycle mains, T = 0-02 seconds, so the peak to peak ripple voltage is 0-02 IjC. For a full-wave system T — 0-01 seconds so the peak to peak ripple is 0-01 //C •wWjIIIIJWa. out Figure Application to signal rectification {Figure )—For signal rectification the load is usually constant and so regulation is not of any importance. Further, power levels are low and there is no question of destroying the diode. We are therefore free to vary C and see how doing this affects the 102
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