Question: The output pulse width from a 74121 OS is given by the approximate formula tp 0.7R T C T where R T is the
The output pulse width from a 74121 OS is given by the approximate formula tp ≈ 0.7RTCT where RT is the resistance connected between the REXT/CEXT pin and VCC, and CT is the capacitance connected between the CEXT pin and the REXT/CEXT pin. The value for RT can be varied between 2 and 40 kΩ, and CT can be as large as 1000 μF.
(a) Show how a 74121 can be connected to produce a negative-going pulse with a 5-ms duration whenever either of two logic signals (E or F) makes a NGT. Both E and F are normally in the HIGH state.
(b) Modify the circuit so that a control input signal, G, can disable the OS output pulse, regardless of what occurs at E or F.
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