Discussion
The adjustment terminal of LM 317 three terminal variable voltage regulator is bypassed with a capacitor to obtain :
Answer: B
The bypass capacitor gives a very high ripple rejection ratio.
In the LM317 the reference voltage sits between the output and the adjustment terminal, and the adjustment pin is fed from a resistive divider. Ripple on the output is fed back through that divider and amplified along with the reference. A capacitor of about 10 μF from the adjustment pin to ground bypasses the ripple, and the datasheet shows the ripple rejection rising from about 65 dB to about 80 dB.
The purpose is the opposite of low ripple rejection. Transient response is handled mainly by the output capacitor, and the capacitor does not create a high impedance.
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