Pulse and Digital Circuits

12.3 IMPROVING SWEEP LINEARITY

A simple exponential sweep generator shown in Fig. 12.9(a) essentially produces a non-linear sweep voltage, unless τ >> T_S or V >>V_s. In an exponential sweep generator, since the capacitor charges exponentially, the resultant sweep so generated is non-linear. To get a linear sweep, the capacitor is required to charge with a constant current. Let us consider the methods of linearizing an exponential sweep. Introduce an auxiliary generator, v, as shown in Fig. 12.9(b). If v is always kept equal to the voltage across C(i.e.,v = v_C), as the polarities of v and v_C are opposite, the net voltage in the loop is V. Then i = V /R which is a constant. That means, the capacitor charging current is constant and perfect linearity ...