Pulse and Digital Circuits

6.7 LATCHING IN A TRANSISTOR SWITCH

The transistor switch is driven into saturation, when ON and into cut-off when OFF, so that the operating point shifts from one extremity to the other as shown in Fig. 6.43.

Through the application of proper signal, the transistor switch is driven into saturation (point S), the intersection of the dc load line and the output characteristic for I_B = I_B(sat). Now by the application of a signal of opposite polarity, the switch can be driven into the OFF state (point O) and the intersection of the dc load line and the output characteristic for I_B = 0. However, when breakdown occurs, the sustaining voltage is the latching voltage V_L. When the device switches from ON to OFF, the operating point is expected to move ...