Dynamically Bootstrapped High Voltage Driver With Isolation
Original Publication Date: 1983-Oct-01
Included in the Prior Art Database: 2005-Feb-07
The circuit shown above is capable of driving high capacitive or resistive loads with low switching current drain. It utilizes logic level switching control and an isolated bootstrapped capacitor. In the figure, devices Q1, Q2, Q3 and Q4 act together to provide a signal at node 2 in phase with the eventual output signal at node 4. When the input signal is at a low level, the bootstrapped capacitor 5 will be discharged. Device Q8 will be off since its gate voltage will be low. Thus, there will be no conduction path from the +V supply to the output or to ground. When it is desired to drive the output to a high level, the input is raised, turning on device Q6 and charging node 3 quickly to the +V -1 threshold voltage level. This voltage appears across the bootstrap capacitor 5.