Three-State Feature Fet-Level Push-Pull Driver
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-07
The three-state push-pull driver shown in the diagram comprises a standard push-pull totem-pole driver circuit to which the new three-state feature (shown within the dashed lines) has been added. Transistors T4, T5, T6 and T7 make up the totem-pole driver, whose signal input is at node A and whose output is at node 1/. The high impedance output state is achieved by simultaneously turning off transistors T4 and T5. T4 then causes transistor T7 to turn off, giving the desired high impedance. The high impedance state is controlled by a single active-low signal applied at node C. When node C is either floating or at an up level (logical "1"), the three-state feature is deactivated, and the push-pull driver can be operated as a normal inverter.